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	$55.72	11.148%	$61.9317	$61.93	$61.95	$61.90
Purchase #2	$143.32	11.367%	$159.6112	$159.61	$159.60	$159.60
Purchase #3	$106.92	10.654%	$118.3113	$118.31	$118.30	$118.30
Purchase #4	$52.36	11.703%	$58.4877	$58.49	$58.50	$58.50
Purchase #5	$83.33	9.404%	$91.1664	$91.17	$91.15	$91.20
Purchase #6	$131.73	10.816%	$145.9779	$145.98	$146.00	$146.00
Purchase #7	$40.47	12.392%	$45.485	$45.49	$45.50	$45.50
7 purchase totals =	$613.85		$680.9712	$680.98	$681.00	$681.00