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	$78.78	9.817%	$86.5138	$86.51	$86.50	$86.50
Purchase #2	$33.37	11.701%	$37.2746	$37.27	$37.25	$37.30
Purchase #3	$6.42	11.366%	$7.1497	$7.15	$7.15	$7.10
Purchase #4	$6.32	11.786%	$7.0649	$7.06	$7.05	$7.10
Purchase #5	$248.50	6.304%	$264.1654	$264.17	$264.15	$264.20
Purchase #6	$31.33	7.382%	$33.6428	$33.64	$33.65	$33.60
Purchase #7	$217.26	3.794%	$225.5028	$225.50	$225.50	$225.50
7 purchase totals =	$621.98		$661.3140	$661.30	$661.25	$661.30