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	$248.38	10.710%	$274.9815	$274.98	$275.00	$275.00
Purchase #2	$205.60	13.512%	$233.3807	$233.38	$233.40	$233.40
Purchase #3	$35.82	10.375%	$39.5363	$39.54	$39.55	$39.50
Purchase #4	$179.80	3.536%	$186.1577	$186.16	$186.15	$186.20
Purchase #5	$148.91	13.495%	$169.0054	$169.01	$169.00	$169.00
Purchase #6	$66.32	8.651%	$72.0573	$72.06	$72.05	$72.10
Purchase #7	$82.73	12.612%	$93.1639	$93.16	$93.15	$93.20
7 purchase totals =	$967.56		$1,068.2828	$1,068.29	$1,068.30	$1,068.40