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	$151.76	5.241%	$159.7137	$159.71	$159.70	$159.70
Purchase #2	$195.38	13.707%	$222.1607	$222.16	$222.15	$222.20
Purchase #3	$187.54	7.433%	$201.4798	$201.48	$201.50	$201.50
Purchase #4	$202.42	13.577%	$229.9026	$229.90	$229.90	$229.90
Purchase #5	$19.56	3.836%	$20.3103	$20.31	$20.30	$20.30
Purchase #6	$249.90	5.867%	$264.5616	$264.56	$264.55	$264.60
Purchase #7	$95.25	3.728%	$98.8009	$98.80	$98.80	$98.80
7 purchase totals =	$1,101.81		$1,196.9296	$1,196.92	$1,196.90	$1,197.00