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	$20.33	9.838%	$22.3301	$22.33	$22.35	$22.30
Purchase #2	$211.30	5.831%	$223.6209	$223.62	$223.60	$223.60
Purchase #3	$71.34	9.365%	$78.021	$78.02	$78.00	$78.00
Purchase #4	$45.52	13.574%	$51.6989	$51.70	$51.70	$51.70
Purchase #5	$52.31	9.796%	$57.4343	$57.43	$57.45	$57.40
Purchase #6	$67.33	7.197%	$72.1757	$72.18	$72.20	$72.20
Purchase #7	$187.48	10.117%	$206.4474	$206.45	$206.45	$206.40
7 purchase totals =	$655.61		$711.7283	$711.73	$711.75	$711.60