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	$91.42	13.801%	$104.0369	$104.04	$104.05	$104.00
Purchase #2	$31.54	10.254%	$34.7741	$34.77	$34.75	$34.80
Purchase #3	$181.67	3.873%	$188.7061	$188.71	$188.70	$188.70
Purchase #4	$83.89	7.751%	$90.3923	$90.39	$90.40	$90.40
Purchase #5	$77.85	3.361%	$80.4665	$80.47	$80.45	$80.50
Purchase #6	$118.66	3.132%	$122.3764	$122.38	$122.40	$122.40
Purchase #7	$165.33	11.468%	$184.29	$184.29	$184.30	$184.30
7 purchase totals =	$750.36		$805.0423	$805.05	$805.05	$805.10