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	$95.75	9.787%	$105.1211	$105.12	$105.10	$105.10
Purchase #2	$85.51	5.377%	$90.1079	$90.11	$90.10	$90.10
Purchase #3	$233.61	6.290%	$248.3041	$248.30	$248.30	$248.30
Purchase #4	$248.84	5.739%	$263.1209	$263.12	$263.10	$263.10
Purchase #5	$221.43	12.412%	$248.9139	$248.91	$248.90	$248.90
Purchase #6	$30.48	5.760%	$32.2356	$32.24	$32.25	$32.20
Purchase #7	$100.68	7.344%	$108.0739	$108.07	$108.05	$108.10
7 purchase totals =	$1,016.30		$1,095.8774	$1,095.87	$1,095.80	$1,095.80