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	$65.76	10.177%	$72.4524	$72.45	$72.45	$72.50
Purchase #2	$95.34	13.760%	$108.4588	$108.46	$108.45	$108.50
Purchase #3	$56.31	3.630%	$58.3541	$58.35	$58.35	$58.40
Purchase #4	$201.47	11.147%	$223.9279	$223.93	$223.95	$223.90
Purchase #5	$57.38	6.524%	$61.1235	$61.12	$61.10	$61.10
Purchase #6	$238.60	6.147%	$253.2667	$253.27	$253.25	$253.30
Purchase #7	$110.72	12.494%	$124.5534	$124.55	$124.55	$124.60
7 purchase totals =	$825.58		$902.1368	$902.13	$902.10	$902.30