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	$57.45	9.250%	$62.7641	$62.76	$62.75	$62.80
Purchase #2	$118.90	7.161%	$127.4144	$127.41	$127.40	$127.40
Purchase #3	$169.59	12.306%	$190.4597	$190.46	$190.45	$190.50
Purchase #4	$27.52	5.864%	$29.1338	$29.13	$29.15	$29.10
Purchase #5	$202.91	11.279%	$225.7962	$225.80	$225.80	$225.80
Purchase #6	$51.76	5.410%	$54.5602	$54.56	$54.55	$54.60
Purchase #7	$182.39	12.355%	$204.9243	$204.92	$204.90	$204.90
7 purchase totals =	$810.52		$895.0527	$895.04	$895.00	$895.10