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	$224.98	12.600%	$253.3275	$253.33	$253.35	$253.30
Purchase #2	$180.51	8.730%	$196.2685	$196.27	$196.25	$196.30
Purchase #3	$79.77	8.716%	$86.7228	$86.72	$86.70	$86.70
Purchase #4	$212.81	7.369%	$228.492	$228.49	$228.50	$228.50
Purchase #5	$139.66	6.600%	$148.8776	$148.88	$148.90	$148.90
Purchase #6	$35.54	8.289%	$38.4859	$38.49	$38.50	$38.50
Purchase #7	$200.92	7.347%	$215.6816	$215.68	$215.70	$215.70
7 purchase totals =	$1,074.19		$1,167.8559	$1,167.86	$1,167.90	$1,167.90