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	$55.25	11.389%	$61.5424	$61.54	$61.55	$61.50
Purchase #2	$168.91	7.451%	$181.4955	$181.50	$181.50	$181.50
Purchase #3	$89.41	12.780%	$100.8366	$100.84	$100.85	$100.80
Purchase #4	$160.45	8.639%	$174.3113	$174.31	$174.30	$174.30
Purchase #5	$188.72	11.175%	$209.8095	$209.81	$209.80	$209.80
Purchase #6	$95.88	10.196%	$105.6559	$105.66	$105.65	$105.70
Purchase #7	$54.56	11.250%	$60.698	$60.70	$60.70	$60.70
7 purchase totals =	$813.18		$894.3492	$894.36	$894.35	$894.30