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	$30.47	4.826%	$31.9405	$31.94	$31.95	$31.90
Purchase #2	$171.65	13.221%	$194.3438	$194.34	$194.35	$194.30
Purchase #3	$90.76	4.843%	$95.1555	$95.16	$95.15	$95.20
Purchase #4	$45.42	12.587%	$51.137	$51.14	$51.15	$51.10
Purchase #5	$99.64	4.564%	$104.1876	$104.19	$104.20	$104.20
Purchase #6	$152.87	7.465%	$164.2817	$164.28	$164.30	$164.30
Purchase #7	$100.87	10.445%	$111.4059	$111.41	$111.40	$111.40
7 purchase totals =	$691.68		$752.4520	$752.46	$752.50	$752.40