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	$247.32	7.188%	$265.0974	$265.10	$265.10	$265.10
Purchase #2	$80.79	10.552%	$89.315	$89.32	$89.30	$89.30
Purchase #3	$96.89	10.244%	$106.8154	$106.82	$106.80	$106.80
Purchase #4	$188.79	10.828%	$209.2322	$209.23	$209.25	$209.20
Purchase #5	$220.33	9.629%	$241.5456	$241.55	$241.55	$241.50
Purchase #6	$45.71	9.465%	$50.0365	$50.04	$50.05	$50.00
Purchase #7	$189.27	7.338%	$203.1586	$203.16	$203.15	$203.20
7 purchase totals =	$1,069.10		$1,165.2007	$1,165.22	$1,165.20	$1,165.10