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	$199.86	11.158%	$222.1604	$222.16	$222.15	$222.20
Purchase #2	$81.87	5.627%	$86.4768	$86.48	$86.50	$86.50
Purchase #3	$48.48	10.364%	$53.5045	$53.50	$53.50	$53.50
Purchase #4	$128.32	6.693%	$136.9085	$136.91	$136.90	$136.90
Purchase #5	$130.88	12.585%	$147.3512	$147.35	$147.35	$147.40
Purchase #6	$45.93	5.249%	$48.3409	$48.34	$48.35	$48.30
Purchase #7	$35.77	4.396%	$37.3424	$37.34	$37.35	$37.30
7 purchase totals =	$671.11		$732.0847	$732.08	$732.10	$732.10