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	$105.78	10.746%	$117.1471	$117.15	$117.15	$117.10
Purchase #2	$53.94	9.631%	$59.135	$59.14	$59.15	$59.10
Purchase #3	$53.58	11.487%	$59.7347	$59.73	$59.75	$59.70
Purchase #4	$139.54	9.164%	$152.3274	$152.33	$152.35	$152.30
Purchase #5	$199.70	9.225%	$218.1223	$218.12	$218.10	$218.10
Purchase #6	$6.25	10.448%	$6.903	$6.90	$6.90	$6.90
Purchase #7	$20.58	8.762%	$22.3832	$22.38	$22.40	$22.40
7 purchase totals =	$579.37		$635.7527	$635.75	$635.80	$635.60