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	$87.29	11.104%	$96.9827	$96.98	$97.00	$97.00
Purchase #2	$37.58	10.422%	$41.4966	$41.50	$41.50	$41.50
Purchase #3	$163.64	9.281%	$178.8274	$178.83	$178.85	$178.80
Purchase #4	$106.38	13.165%	$120.3849	$120.38	$120.40	$120.40
Purchase #5	$11.38	4.191%	$11.8569	$11.86	$11.85	$11.90
Purchase #6	$130.98	6.543%	$139.55	$139.55	$139.55	$139.60
Purchase #7	$132.73	4.815%	$139.1209	$139.12	$139.10	$139.10
7 purchase totals =	$669.98		$728.2194	$728.22	$728.25	$728.30