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	$99.66	5.414%	$105.0556	$105.06	$105.05	$105.10
Purchase #2	$37.28	13.576%	$42.3411	$42.34	$42.35	$42.30
Purchase #3	$123.54	10.415%	$136.4067	$136.41	$136.40	$136.40
Purchase #4	$100.94	12.424%	$113.4808	$113.48	$113.50	$113.50
Purchase #5	$68.61	12.342%	$77.0778	$77.08	$77.10	$77.10
Purchase #6	$120.35	6.446%	$128.1078	$128.11	$128.10	$128.10
Purchase #7	$91.33	9.122%	$99.6611	$99.66	$99.65	$99.70
7 purchase totals =	$641.71		$702.1309	$702.14	$702.15	$702.20