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	$129.48	11.613%	$144.5165	$144.52	$144.50	$144.50
Purchase #2	$117.29	11.631%	$130.932	$130.93	$130.95	$130.90
Purchase #3	$166.90	4.536%	$174.4706	$174.47	$174.45	$174.50
Purchase #4	$248.33	4.399%	$259.254	$259.25	$259.25	$259.30
Purchase #5	$233.57	7.457%	$250.9873	$250.99	$251.00	$251.00
Purchase #6	$75.88	9.250%	$82.8989	$82.90	$82.90	$82.90
Purchase #7	$36.99	6.380%	$39.35	$39.35	$39.35	$39.40
7 purchase totals =	$1,008.44		$1,082.4093	$1,082.41	$1,082.40	$1,082.50