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	$54.66	12.213%	$61.3356	$61.34	$61.35	$61.30
Purchase #2	$229.94	6.849%	$245.6886	$245.69	$245.70	$245.70
Purchase #3	$40.64	11.174%	$45.1811	$45.18	$45.20	$45.20
Purchase #4	$204.44	13.129%	$231.2809	$231.28	$231.30	$231.30
Purchase #5	$33.68	10.276%	$37.141	$37.14	$37.15	$37.10
Purchase #6	$215.88	4.481%	$225.5536	$225.55	$225.55	$225.60
Purchase #7	$71.33	10.607%	$78.896	$78.90	$78.90	$78.90
7 purchase totals =	$850.57		$925.0768	$925.08	$925.15	$925.10