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	$207.97	7.481%	$223.5282	$223.53	$223.55	$223.50
Purchase #2	$47.83	4.118%	$49.7996	$49.80	$49.80	$49.80
Purchase #3	$106.51	10.362%	$117.5466	$117.55	$117.55	$117.50
Purchase #4	$60.47	6.755%	$64.5547	$64.55	$64.55	$64.60
Purchase #5	$205.57	7.413%	$220.8089	$220.81	$220.80	$220.80
Purchase #6	$81.31	11.627%	$90.7639	$90.76	$90.75	$90.80
Purchase #7	$115.39	11.650%	$128.8329	$128.83	$128.85	$128.80
7 purchase totals =	$825.05		$895.8348	$895.83	$895.85	$895.80