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	$105.63	7.404%	$113.4508	$113.45	$113.45	$113.50
Purchase #2	$211.77	8.395%	$229.5481	$229.55	$229.55	$229.50
Purchase #3	$43.29	3.707%	$44.8948	$44.89	$44.90	$44.90
Purchase #4	$99.69	3.860%	$103.538	$103.54	$103.55	$103.50
Purchase #5	$152.68	11.301%	$169.9344	$169.93	$169.95	$169.90
Purchase #6	$79.42	5.158%	$83.5165	$83.52	$83.50	$83.50
Purchase #7	$32.49	11.799%	$36.3235	$36.32	$36.30	$36.30
7 purchase totals =	$724.97		$781.2061	$781.20	$781.20	$781.10