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	$196.35	9.799%	$215.5903	$215.59	$215.60	$215.60
Purchase #2	$84.55	13.334%	$95.8239	$95.82	$95.80	$95.80
Purchase #3	$204.68	10.242%	$225.6433	$225.64	$225.65	$225.60
Purchase #4	$77.93	3.778%	$80.8742	$80.87	$80.85	$80.90
Purchase #5	$156.46	3.482%	$161.9079	$161.91	$161.90	$161.90
Purchase #6	$77.74	9.640%	$85.2341	$85.23	$85.25	$85.20
Purchase #7	$229.56	4.727%	$240.4113	$240.41	$240.40	$240.40
7 purchase totals =	$1,027.27		$1,105.4850	$1,105.47	$1,105.45	$1,105.40