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	$197.40	9.477%	$216.1076	$216.11	$216.10	$216.10
Purchase #2	$142.91	4.822%	$149.8011	$149.80	$149.80	$149.80
Purchase #3	$55.47	10.838%	$61.4818	$61.48	$61.50	$61.50
Purchase #4	$53.52	3.639%	$55.4676	$55.47	$55.45	$55.50
Purchase #5	$67.72	7.386%	$72.7218	$72.72	$72.70	$72.70
Purchase #6	$13.31	12.846%	$15.0198	$15.02	$15.00	$15.00
Purchase #7	$165.93	3.137%	$171.1352	$171.14	$171.15	$171.10
7 purchase totals =	$696.26		$741.7349	$741.74	$741.70	$741.70