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	$98.93	11.632%	$110.4375	$110.44	$110.45	$110.40
Purchase #2	$98.46	3.441%	$101.848	$101.85	$101.85	$101.80
Purchase #3	$247.97	6.375%	$263.7781	$263.78	$263.80	$263.80
Purchase #4	$168.80	9.210%	$184.3465	$184.35	$184.35	$184.30
Purchase #5	$92.98	8.339%	$100.7336	$100.73	$100.75	$100.70
Purchase #6	$216.53	4.175%	$225.5701	$225.57	$225.55	$225.60
Purchase #7	$86.85	4.353%	$90.6306	$90.63	$90.65	$90.60
7 purchase totals =	$1,010.52		$1,077.3444	$1,077.35	$1,077.40	$1,077.20