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	$226.66	12.268%	$254.4666	$254.47	$254.45	$254.50
Purchase #2	$250.30	7.872%	$270.0036	$270.00	$270.00	$270.00
Purchase #3	$36.71	6.516%	$39.102	$39.10	$39.10	$39.10
Purchase #4	$19.85	5.862%	$21.0136	$21.01	$21.00	$21.00
Purchase #5	$231.27	13.668%	$262.88	$262.88	$262.90	$262.90
Purchase #6	$121.71	6.358%	$129.4483	$129.45	$129.45	$129.40
Purchase #7	$37.79	11.853%	$42.2692	$42.27	$42.25	$42.30
7 purchase totals =	$924.29		$1,019.1833	$1,019.18	$1,019.15	$1,019.20