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	$185.27	10.440%	$204.6122	$204.61	$204.60	$204.60
Purchase #2	$37.58	11.502%	$41.9025	$41.90	$41.90	$41.90
Purchase #3	$128.39	10.114%	$141.3754	$141.38	$141.40	$141.40
Purchase #4	$12.46	8.346%	$13.4999	$13.50	$13.50	$13.50
Purchase #5	$105.70	5.305%	$111.3074	$111.31	$111.30	$111.30
Purchase #6	$211.28	5.243%	$222.3574	$222.36	$222.35	$222.40
Purchase #7	$13.60	4.518%	$14.2144	$14.21	$14.20	$14.20
7 purchase totals =	$694.28		$749.2692	$749.27	$749.25	$749.30