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	$120.44	3.643%	$124.8276	$124.83	$124.85	$124.80
Purchase #2	$69.62	3.384%	$71.9759	$71.98	$72.00	$72.00
Purchase #3	$100.59	6.693%	$107.3225	$107.32	$107.30	$107.30
Purchase #4	$93.46	7.686%	$100.6433	$100.64	$100.65	$100.60
Purchase #5	$162.92	10.311%	$179.7187	$179.72	$179.70	$179.70
Purchase #6	$79.88	3.810%	$82.9234	$82.92	$82.90	$82.90
Purchase #7	$120.55	8.451%	$130.7377	$130.74	$130.75	$130.70
7 purchase totals =	$747.46		$798.1491	$798.15	$798.15	$798.00