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	$90.45	8.501%	$98.1392	$98.14	$98.15	$98.10
Purchase #2	$66.30	4.755%	$69.4526	$69.45	$69.45	$69.50
Purchase #3	$71.58	7.654%	$77.0587	$77.06	$77.05	$77.10
Purchase #4	$136.98	11.106%	$152.193	$152.19	$152.20	$152.20
Purchase #5	$230.46	10.781%	$255.3059	$255.31	$255.30	$255.30
Purchase #6	$226.92	12.685%	$255.7048	$255.70	$255.70	$255.70
Purchase #7	$221.73	9.726%	$243.2955	$243.30	$243.30	$243.30
7 purchase totals =	$1,044.42		$1,151.1497	$1,151.15	$1,151.15	$1,151.20