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	$72.86	4.759%	$76.3274	$76.33	$76.35	$76.30
Purchase #2	$47.75	13.533%	$54.212	$54.21	$54.20	$54.20
Purchase #3	$72.80	12.779%	$82.1031	$82.10	$82.10	$82.10
Purchase #4	$127.57	12.703%	$143.7752	$143.78	$143.80	$143.80
Purchase #5	$26.69	11.465%	$29.75	$29.75	$29.75	$29.80
Purchase #6	$11.58	5.685%	$12.2383	$12.24	$12.25	$12.20
Purchase #7	$47.74	12.736%	$53.8202	$53.82	$53.80	$53.80
7 purchase totals =	$406.99		$452.2262	$452.23	$452.25	$452.20