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	$110.63	12.153%	$124.0749	$124.07	$124.05	$124.10
Purchase #2	$49.73	7.152%	$53.2867	$53.29	$53.30	$53.30
Purchase #3	$73.94	8.761%	$80.4179	$80.42	$80.40	$80.40
Purchase #4	$230.37	10.159%	$253.7733	$253.77	$253.75	$253.80
Purchase #5	$89.89	11.719%	$100.4242	$100.42	$100.40	$100.40
Purchase #6	$222.33	3.134%	$229.2978	$229.30	$229.30	$229.30
Purchase #7	$196.25	5.692%	$207.4206	$207.42	$207.40	$207.40
7 purchase totals =	$973.14		$1,048.6954	$1,048.69	$1,048.60	$1,048.70