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	$228.26	13.663%	$259.4472	$259.45	$259.45	$259.40
Purchase #2	$122.42	5.251%	$128.8483	$128.85	$128.85	$128.80
Purchase #3	$49.91	6.642%	$53.225	$53.23	$53.25	$53.20
Purchase #4	$250.81	6.449%	$266.9847	$266.98	$267.00	$267.00
Purchase #5	$244.57	5.786%	$258.7208	$258.72	$258.70	$258.70
Purchase #6	$73.53	5.245%	$77.3866	$77.39	$77.40	$77.40
Purchase #7	$88.90	11.525%	$99.1457	$99.15	$99.15	$99.10
7 purchase totals =	$1,058.40		$1,143.7583	$1,143.77	$1,143.80	$1,143.60