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	$41.64	13.185%	$47.1302	$47.13	$47.15	$47.10
Purchase #2	$98.31	13.712%	$111.7903	$111.79	$111.80	$111.80
Purchase #3	$165.48	12.500%	$186.165	$186.17	$186.15	$186.20
Purchase #4	$119.26	3.270%	$123.1598	$123.16	$123.15	$123.20
Purchase #5	$170.97	11.549%	$190.7153	$190.72	$190.70	$190.70
Purchase #6	$84.79	4.679%	$88.7573	$88.76	$88.75	$88.80
Purchase #7	$143.44	3.461%	$148.4045	$148.40	$148.40	$148.40
7 purchase totals =	$823.89		$896.1224	$896.13	$896.10	$896.20