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	$100.28	4.154%	$104.4456	$104.45	$104.45	$104.40
Purchase #2	$33.51	12.219%	$37.6046	$37.60	$37.60	$37.60
Purchase #3	$178.90	7.546%	$192.3998	$192.40	$192.40	$192.40
Purchase #4	$89.33	6.634%	$95.2562	$95.26	$95.25	$95.30
Purchase #5	$154.89	7.118%	$165.9151	$165.92	$165.90	$165.90
Purchase #6	$168.70	12.203%	$189.2865	$189.29	$189.30	$189.30
Purchase #7	$203.50	3.207%	$210.0262	$210.03	$210.05	$210.00
7 purchase totals =	$929.11		$994.9340	$994.95	$994.95	$994.90