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	$56.87	6.282%	$60.4426	$60.44	$60.45	$60.40
Purchase #2	$225.83	9.695%	$247.7242	$247.72	$247.70	$247.70
Purchase #3	$127.65	7.674%	$137.4459	$137.45	$137.45	$137.40
Purchase #4	$210.31	7.443%	$225.9634	$225.96	$225.95	$226.00
Purchase #5	$209.73	6.593%	$223.5575	$223.56	$223.55	$223.60
Purchase #6	$197.96	6.751%	$211.3243	$211.32	$211.30	$211.30
Purchase #7	$134.25	12.139%	$150.5466	$150.55	$150.55	$150.50
7 purchase totals =	$1,162.60		$1,257.0045	$1,257.00	$1,256.95	$1,256.90