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	$200.67	4.319%	$209.3369	$209.34	$209.35	$209.30
Purchase #2	$238.72	10.777%	$264.4469	$264.45	$264.45	$264.40
Purchase #3	$207.26	6.622%	$220.9848	$220.98	$221.00	$221.00
Purchase #4	$85.64	6.760%	$91.4293	$91.43	$91.45	$91.40
Purchase #5	$18.80	8.161%	$20.3343	$20.33	$20.35	$20.30
Purchase #6	$193.51	10.325%	$213.4899	$213.49	$213.50	$213.50
Purchase #7	$36.73	7.251%	$39.3933	$39.39	$39.40	$39.40
7 purchase totals =	$981.33		$1,059.4154	$1,059.41	$1,059.50	$1,059.30