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	$159.63	7.268%	$171.2319	$171.23	$171.25	$171.20
Purchase #2	$67.54	4.866%	$70.8265	$70.83	$70.85	$70.80
Purchase #3	$190.93	3.867%	$198.3133	$198.31	$198.30	$198.30
Purchase #4	$88.55	3.293%	$91.466	$91.47	$91.45	$91.50
Purchase #5	$216.83	6.182%	$230.2344	$230.23	$230.25	$230.20
Purchase #6	$182.26	3.768%	$189.1276	$189.13	$189.15	$189.10
Purchase #7	$194.62	13.832%	$221.5398	$221.54	$221.55	$221.50
7 purchase totals =	$1,100.36		$1,172.7395	$1,172.74	$1,172.80	$1,172.60