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	$195.91	13.521%	$222.399	$222.40	$222.40	$222.40
Purchase #2	$65.65	3.459%	$67.9208	$67.92	$67.90	$67.90
Purchase #3	$127.81	4.591%	$133.6778	$133.68	$133.70	$133.70
Purchase #4	$221.53	3.560%	$229.4165	$229.42	$229.40	$229.40
Purchase #5	$80.69	11.321%	$89.8249	$89.82	$89.80	$89.80
Purchase #6	$60.30	3.844%	$62.6179	$62.62	$62.60	$62.60
Purchase #7	$153.62	11.355%	$171.0636	$171.06	$171.05	$171.10
7 purchase totals =	$905.51		$976.9205	$976.92	$976.85	$976.90