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	$23.41	6.147%	$24.849	$24.85	$24.85	$24.80
Purchase #2	$45.33	4.796%	$47.504	$47.50	$47.50	$47.50
Purchase #3	$93.69	5.333%	$98.6865	$98.69	$98.70	$98.70
Purchase #4	$62.39	12.415%	$70.1357	$70.14	$70.15	$70.10
Purchase #5	$165.77	13.471%	$188.1009	$188.10	$188.10	$188.10
Purchase #6	$44.52	13.711%	$50.6241	$50.62	$50.60	$50.60
Purchase #7	$97.72	6.480%	$104.0523	$104.05	$104.05	$104.10
7 purchase totals =	$532.83		$583.9525	$583.95	$583.95	$583.90