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	$42.52	6.254%	$45.1792	$45.18	$45.20	$45.20
Purchase #2	$53.82	10.691%	$59.5739	$59.57	$59.55	$59.60
Purchase #3	$96.26	12.550%	$108.3406	$108.34	$108.35	$108.30
Purchase #4	$91.56	9.461%	$100.2225	$100.22	$100.20	$100.20
Purchase #5	$69.42	9.756%	$76.1926	$76.19	$76.20	$76.20
Purchase #6	$155.39	7.655%	$167.2851	$167.29	$167.30	$167.30
Purchase #7	$140.46	4.732%	$147.1066	$147.11	$147.10	$147.10
7 purchase totals =	$649.43		$703.9005	$703.90	$703.90	$703.90