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	$243.37	10.640%	$269.2646	$269.26	$269.25	$269.30
Purchase #2	$82.46	12.138%	$92.469	$92.47	$92.45	$92.50
Purchase #3	$206.77	10.631%	$228.7517	$228.75	$228.75	$228.80
Purchase #4	$47.58	3.199%	$49.1021	$49.10	$49.10	$49.10
Purchase #5	$11.35	3.872%	$11.7895	$11.79	$11.80	$11.80
Purchase #6	$179.42	9.567%	$196.5851	$196.59	$196.60	$196.60
Purchase #7	$145.62	9.408%	$159.3199	$159.32	$159.30	$159.30
7 purchase totals =	$916.57		$1,007.2819	$1,007.28	$1,007.25	$1,007.40