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	$115.89	3.165%	$119.5579	$119.56	$119.55	$119.60
Purchase #2	$114.55	7.728%	$123.4024	$123.40	$123.40	$123.40
Purchase #3	$55.77	6.759%	$59.5395	$59.54	$59.55	$59.50
Purchase #4	$21.92	4.405%	$22.8856	$22.89	$22.90	$22.90
Purchase #5	$156.35	7.178%	$167.5728	$167.57	$167.55	$167.60
Purchase #6	$77.36	4.753%	$81.0369	$81.04	$81.05	$81.00
Purchase #7	$158.95	8.739%	$172.8406	$172.84	$172.85	$172.80
7 purchase totals =	$700.79		$746.8357	$746.84	$746.85	$746.80