Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$169.58	12.289%	$190.4197	$190.42	$190.40	$190.40
Purchase #2	$174.33	4.871%	$182.8216	$182.82	$182.80	$182.80
Purchase #3	$148.71	5.198%	$156.4399	$156.44	$156.45	$156.40
Purchase #4	$186.44	10.351%	$205.7384	$205.74	$205.75	$205.70
Purchase #5	$183.41	11.456%	$204.4214	$204.42	$204.40	$204.40
Purchase #6	$178.59	6.613%	$190.4002	$190.40	$190.40	$190.40
Purchase #7	$156.41	9.351%	$171.0359	$171.04	$171.05	$171.00
7 purchase totals =	$1,197.47		$1,301.2771	$1,301.28	$1,301.25	$1,301.10