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	$72.28	6.210%	$76.7686	$76.77	$76.75	$76.80
Purchase #2	$244.36	13.570%	$277.5197	$277.52	$277.50	$277.50
Purchase #3	$133.90	13.692%	$152.2336	$152.23	$152.25	$152.20
Purchase #4	$104.95	7.510%	$112.8317	$112.83	$112.85	$112.80
Purchase #5	$27.51	7.633%	$29.6098	$29.61	$29.60	$29.60
Purchase #6	$42.44	13.831%	$48.3099	$48.31	$48.30	$48.30
Purchase #7	$31.71	11.117%	$35.2352	$35.24	$35.25	$35.20
7 purchase totals =	$657.15		$732.5085	$732.51	$732.50	$732.40