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	$233.82	9.442%	$255.8973	$255.90	$255.90	$255.90
Purchase #2	$119.47	9.752%	$131.1207	$131.12	$131.10	$131.10
Purchase #3	$28.50	5.562%	$30.0852	$30.09	$30.10	$30.10
Purchase #4	$212.31	4.573%	$222.0189	$222.02	$222.00	$222.00
Purchase #5	$37.93	13.690%	$43.1226	$43.12	$43.10	$43.10
Purchase #6	$202.69	4.803%	$212.4252	$212.43	$212.45	$212.40
Purchase #7	$150.33	8.308%	$162.8194	$162.82	$162.80	$162.80
7 purchase totals =	$985.05		$1,057.4893	$1,057.50	$1,057.45	$1,057.40