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	$222.71	9.301%	$243.4243	$243.42	$243.40	$243.40
Purchase #2	$135.78	8.850%	$147.7965	$147.80	$147.80	$147.80
Purchase #3	$88.64	11.436%	$98.7769	$98.78	$98.80	$98.80
Purchase #4	$172.47	9.465%	$188.7943	$188.79	$188.80	$188.80
Purchase #5	$94.51	5.241%	$99.4633	$99.46	$99.45	$99.50
Purchase #6	$180.49	4.674%	$188.9261	$188.93	$188.95	$188.90
Purchase #7	$67.35	6.419%	$71.6732	$71.67	$71.65	$71.70
7 purchase totals =	$961.95		$1,038.8546	$1,038.85	$1,038.85	$1,038.90