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	$222.95	10.302%	$245.9183	$245.92	$245.90	$245.90
Purchase #2	$243.84	9.282%	$266.4732	$266.47	$266.45	$266.50
Purchase #3	$143.85	5.132%	$151.2324	$151.23	$151.25	$151.20
Purchase #4	$138.83	12.204%	$155.7728	$155.77	$155.75	$155.80
Purchase #5	$92.35	9.637%	$101.2498	$101.25	$101.25	$101.20
Purchase #6	$56.37	10.395%	$62.2297	$62.23	$62.25	$62.20
Purchase #7	$115.54	11.534%	$128.8664	$128.87	$128.85	$128.90
7 purchase totals =	$1,013.73		$1,111.7426	$1,111.74	$1,111.70	$1,111.70