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	$94.99	5.160%	$99.8915	$99.89	$99.90	$99.90
Purchase #2	$111.43	13.867%	$126.882	$126.88	$126.90	$126.90
Purchase #3	$195.99	7.484%	$210.6579	$210.66	$210.65	$210.70
Purchase #4	$165.36	9.394%	$180.8939	$180.89	$180.90	$180.90
Purchase #5	$62.89	7.656%	$67.7049	$67.70	$67.70	$67.70
Purchase #6	$90.40	4.684%	$94.6343	$94.63	$94.65	$94.60
Purchase #7	$228.75	4.456%	$238.9431	$238.94	$238.95	$238.90
7 purchase totals =	$949.81		$1,019.6076	$1,019.59	$1,019.65	$1,019.60