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	$136.80	11.199%	$152.1202	$152.12	$152.10	$152.10
Purchase #2	$85.46	4.592%	$89.3843	$89.38	$89.40	$89.40
Purchase #3	$160.93	5.593%	$169.9308	$169.93	$169.95	$169.90
Purchase #4	$111.73	11.259%	$124.3097	$124.31	$124.30	$124.30
Purchase #5	$14.71	5.238%	$15.4805	$15.48	$15.50	$15.50
Purchase #6	$139.27	4.464%	$145.487	$145.49	$145.50	$145.50
Purchase #7	$126.47	7.326%	$135.7352	$135.74	$135.75	$135.70
7 purchase totals =	$775.37		$832.4477	$832.45	$832.50	$832.40