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	$164.26	12.339%	$184.528	$184.53	$184.55	$184.50
Purchase #2	$225.45	6.581%	$240.2869	$240.29	$240.30	$240.30
Purchase #3	$244.57	9.314%	$267.3492	$267.35	$267.35	$267.30
Purchase #4	$20.59	6.433%	$21.9146	$21.91	$21.90	$21.90
Purchase #5	$89.69	4.296%	$93.5431	$93.54	$93.55	$93.50
Purchase #6	$211.48	11.728%	$236.2824	$236.28	$236.30	$236.30
Purchase #7	$103.67	3.135%	$106.9201	$106.92	$106.90	$106.90
7 purchase totals =	$1,059.71		$1,150.8243	$1,150.82	$1,150.85	$1,150.70