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	$158.52	13.142%	$179.3527	$179.35	$179.35	$179.40
Purchase #2	$57.26	9.260%	$62.5623	$62.56	$62.55	$62.60
Purchase #3	$191.94	3.427%	$198.5178	$198.52	$198.50	$198.50
Purchase #4	$185.27	7.827%	$199.7711	$199.77	$199.75	$199.80
Purchase #5	$103.95	5.261%	$109.4188	$109.42	$109.40	$109.40
Purchase #6	$129.73	7.562%	$139.5402	$139.54	$139.55	$139.50
Purchase #7	$135.27	6.533%	$144.1072	$144.11	$144.10	$144.10
7 purchase totals =	$961.94		$1,033.2701	$1,033.27	$1,033.20	$1,033.30