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	$120.44	8.549%	$130.7364	$130.74	$130.75	$130.70
Purchase #2	$67.45	7.333%	$72.3961	$72.40	$72.40	$72.40
Purchase #3	$22.89	6.764%	$24.4383	$24.44	$24.45	$24.40
Purchase #4	$163.84	12.537%	$184.3806	$184.38	$184.40	$184.40
Purchase #5	$151.55	3.423%	$156.7376	$156.74	$156.75	$156.70
Purchase #6	$128.32	6.813%	$137.0624	$137.06	$137.05	$137.10
Purchase #7	$171.65	11.139%	$190.7701	$190.77	$190.75	$190.80
7 purchase totals =	$826.14		$896.5215	$896.53	$896.55	$896.50