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	$176.86	5.121%	$185.917	$185.92	$185.90	$185.90
Purchase #2	$234.66	3.538%	$242.9623	$242.96	$242.95	$243.00
Purchase #3	$52.58	12.824%	$59.3229	$59.32	$59.30	$59.30
Purchase #4	$92.50	7.685%	$99.6086	$99.61	$99.60	$99.60
Purchase #5	$201.68	11.562%	$224.9982	$225.00	$225.00	$225.00
Purchase #6	$194.70	3.125%	$200.7844	$200.78	$200.80	$200.80
Purchase #7	$214.47	6.547%	$228.5114	$228.51	$228.50	$228.50
7 purchase totals =	$1,167.45		$1,242.1048	$1,242.10	$1,242.05	$1,242.10