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	$90.33	12.735%	$101.8335	$101.83	$101.85	$101.80
Purchase #2	$61.50	4.820%	$64.4643	$64.46	$64.45	$64.50
Purchase #3	$107.57	5.758%	$113.7639	$113.76	$113.75	$113.80
Purchase #4	$62.56	13.428%	$70.9606	$70.96	$70.95	$71.00
Purchase #5	$207.51	6.558%	$221.1185	$221.12	$221.10	$221.10
Purchase #6	$82.76	11.813%	$92.5364	$92.54	$92.55	$92.50
Purchase #7	$185.59	8.765%	$201.857	$201.86	$201.85	$201.90
7 purchase totals =	$797.82		$866.5342	$866.53	$866.50	$866.60