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	$134.98	4.719%	$141.3497	$141.35	$141.35	$141.30
Purchase #2	$195.61	10.128%	$215.4214	$215.42	$215.40	$215.40
Purchase #3	$42.97	13.197%	$48.6408	$48.64	$48.65	$48.60
Purchase #4	$28.95	13.286%	$32.7963	$32.80	$32.80	$32.80
Purchase #5	$85.25	11.788%	$95.2993	$95.30	$95.30	$95.30
Purchase #6	$215.49	13.218%	$243.9735	$243.97	$243.95	$244.00
Purchase #7	$105.66	5.110%	$111.0592	$111.06	$111.05	$111.10
7 purchase totals =	$808.91		$888.5402	$888.54	$888.50	$888.50