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	$64.43	8.817%	$70.1108	$70.11	$70.10	$70.10
Purchase #2	$222.84	6.254%	$236.7764	$236.78	$236.80	$236.80
Purchase #3	$133.86	12.160%	$150.1374	$150.14	$150.15	$150.10
Purchase #4	$147.40	10.436%	$162.7827	$162.78	$162.80	$162.80
Purchase #5	$92.97	9.355%	$101.6673	$101.67	$101.65	$101.70
Purchase #6	$209.30	11.611%	$233.6018	$233.60	$233.60	$233.60
Purchase #7	$55.43	12.849%	$62.5522	$62.55	$62.55	$62.60
7 purchase totals =	$926.23		$1,017.6286	$1,017.63	$1,017.65	$1,017.70