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	$170.70	11.273%	$189.943	$189.94	$189.95	$189.90
Purchase #2	$114.52	13.595%	$130.089	$130.09	$130.10	$130.10
Purchase #3	$111.52	6.303%	$118.5491	$118.55	$118.55	$118.50
Purchase #4	$152.86	12.244%	$171.5762	$171.58	$171.60	$171.60
Purchase #5	$159.84	5.588%	$168.7719	$168.77	$168.75	$168.80
Purchase #6	$51.90	3.152%	$53.5359	$53.54	$53.55	$53.50
Purchase #7	$187.44	13.577%	$212.8887	$212.89	$212.90	$212.90
7 purchase totals =	$948.78		$1,045.3538	$1,045.36	$1,045.40	$1,045.30