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	$96.96	8.656%	$105.3529	$105.35	$105.35	$105.40
Purchase #2	$48.66	7.650%	$52.3825	$52.38	$52.40	$52.40
Purchase #3	$109.38	7.148%	$117.1985	$117.20	$117.20	$117.20
Purchase #4	$155.44	6.255%	$165.1628	$165.16	$165.15	$165.20
Purchase #5	$202.73	9.532%	$222.0542	$222.05	$222.05	$222.10
Purchase #6	$138.59	8.463%	$150.3189	$150.32	$150.30	$150.30
Purchase #7	$175.55	5.330%	$184.9068	$184.91	$184.90	$184.90
7 purchase totals =	$927.31		$997.3766	$997.37	$997.35	$997.50