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	$132.82	8.591%	$144.2306	$144.23	$144.25	$144.20
Purchase #2	$94.54	11.159%	$105.0897	$105.09	$105.10	$105.10
Purchase #3	$38.43	7.611%	$41.3549	$41.35	$41.35	$41.40
Purchase #4	$207.74	7.619%	$223.5677	$223.57	$223.55	$223.60
Purchase #5	$88.73	8.748%	$96.4921	$96.49	$96.50	$96.50
Purchase #6	$139.33	7.464%	$149.7296	$149.73	$149.75	$149.70
Purchase #7	$99.43	9.142%	$108.5199	$108.52	$108.50	$108.50
7 purchase totals =	$801.02		$868.9845	$868.98	$869.00	$869.00