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	$77.58	7.710%	$83.5614	$83.56	$83.55	$83.60
Purchase #2	$52.76	9.761%	$57.9099	$57.91	$57.90	$57.90
Purchase #3	$204.28	12.357%	$229.5229	$229.52	$229.50	$229.50
Purchase #4	$184.44	11.588%	$205.8129	$205.81	$205.80	$205.80
Purchase #5	$63.80	13.318%	$72.2969	$72.30	$72.30	$72.30
Purchase #6	$153.42	4.366%	$160.1183	$160.12	$160.10	$160.10
Purchase #7	$180.59	13.528%	$205.0202	$205.02	$205.00	$205.00
7 purchase totals =	$916.87		$1,014.2425	$1,014.24	$1,014.15	$1,014.20