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	$235.92	12.272%	$264.8721	$264.87	$264.85	$264.90
Purchase #2	$179.34	7.299%	$192.43	$192.43	$192.45	$192.40
Purchase #3	$116.71	3.191%	$120.4342	$120.43	$120.45	$120.40
Purchase #4	$106.66	10.106%	$117.4391	$117.44	$117.45	$117.40
Purchase #5	$85.37	4.674%	$89.3602	$89.36	$89.35	$89.40
Purchase #6	$147.48	7.251%	$158.1738	$158.17	$158.15	$158.20
Purchase #7	$61.27	6.593%	$65.3095	$65.31	$65.30	$65.30
7 purchase totals =	$932.75		$1,008.0189	$1,008.01	$1,008.00	$1,008.00