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	$96.30	4.645%	$100.7731	$100.77	$100.75	$100.80
Purchase #2	$229.71	4.555%	$240.1733	$240.17	$240.15	$240.20
Purchase #3	$202.84	10.870%	$224.8887	$224.89	$224.90	$224.90
Purchase #4	$43.91	10.142%	$48.3634	$48.36	$48.35	$48.40
Purchase #5	$135.77	9.173%	$148.2242	$148.22	$148.20	$148.20
Purchase #6	$43.93	4.111%	$45.736	$45.74	$45.75	$45.70
Purchase #7	$94.32	13.290%	$106.8551	$106.86	$106.85	$106.90
7 purchase totals =	$846.78		$915.0138	$915.01	$914.95	$915.10