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	$49.41	9.369%	$54.0392	$54.04	$54.05	$54.00
Purchase #2	$71.66	4.756%	$75.0681	$75.07	$75.05	$75.10
Purchase #3	$249.33	9.215%	$272.3058	$272.31	$272.30	$272.30
Purchase #4	$22.43	13.712%	$25.5056	$25.51	$25.50	$25.50
Purchase #5	$81.53	10.128%	$89.7874	$89.79	$89.80	$89.80
Purchase #6	$101.64	10.736%	$112.5521	$112.55	$112.55	$112.60
Purchase #7	$54.53	8.489%	$59.1591	$59.16	$59.15	$59.20
7 purchase totals =	$630.53		$688.4173	$688.43	$688.40	$688.50