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	$214.54	6.373%	$228.2126	$228.21	$228.20	$228.20
Purchase #2	$73.26	12.753%	$82.6028	$82.60	$82.60	$82.60
Purchase #3	$113.26	3.787%	$117.5492	$117.55	$117.55	$117.50
Purchase #4	$170.48	13.397%	$193.3192	$193.32	$193.30	$193.30
Purchase #5	$65.46	3.698%	$67.8807	$67.88	$67.90	$67.90
Purchase #6	$37.91	13.614%	$43.0711	$43.07	$43.05	$43.10
Purchase #7	$66.34	11.379%	$73.8888	$73.89	$73.90	$73.90
7 purchase totals =	$741.25		$806.5244	$806.52	$806.50	$806.50