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	$111.35	10.605%	$123.1587	$123.16	$123.15	$123.20
Purchase #2	$75.72	3.762%	$78.5686	$78.57	$78.55	$78.60
Purchase #3	$93.45	6.841%	$99.8429	$99.84	$99.85	$99.80
Purchase #4	$237.69	6.560%	$253.2825	$253.28	$253.30	$253.30
Purchase #5	$207.68	11.610%	$231.7916	$231.79	$231.80	$231.80
Purchase #6	$38.27	4.450%	$39.973	$39.97	$39.95	$40.00
Purchase #7	$162.48	13.392%	$184.2393	$184.24	$184.25	$184.20
7 purchase totals =	$926.64		$1,010.8566	$1,010.85	$1,010.85	$1,010.90