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	$95.80	4.259%	$99.8801	$99.88	$99.90	$99.90
Purchase #2	$48.25	8.630%	$52.414	$52.41	$52.40	$52.40
Purchase #3	$105.36	6.616%	$112.3306	$112.33	$112.35	$112.30
Purchase #4	$48.37	13.603%	$54.9498	$54.95	$54.95	$54.90
Purchase #5	$244.85	8.781%	$266.3503	$266.35	$266.35	$266.40
Purchase #6	$120.40	6.151%	$127.8058	$127.81	$127.80	$127.80
Purchase #7	$70.61	4.795%	$73.9957	$74.00	$74.00	$74.00
7 purchase totals =	$733.64		$787.7263	$787.73	$787.75	$787.70