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	$232.54	12.395%	$261.3633	$261.36	$261.35	$261.40
Purchase #2	$65.73	3.219%	$67.8458	$67.85	$67.85	$67.80
Purchase #3	$42.49	6.198%	$45.1235	$45.12	$45.10	$45.10
Purchase #4	$200.94	4.591%	$210.1652	$210.17	$210.15	$210.20
Purchase #5	$122.69	10.785%	$135.9221	$135.92	$135.90	$135.90
Purchase #6	$142.30	4.152%	$148.2083	$148.21	$148.20	$148.20
Purchase #7	$243.62	6.277%	$258.912	$258.91	$258.90	$258.90
7 purchase totals =	$1,050.31		$1,127.5402	$1,127.54	$1,127.45	$1,127.50