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	$62.97	11.353%	$70.119	$70.12	$70.10	$70.10
Purchase #2	$6.83	13.386%	$7.7443	$7.74	$7.75	$7.70
Purchase #3	$111.54	13.224%	$126.29	$126.29	$126.30	$126.30
Purchase #4	$165.44	3.459%	$171.1626	$171.16	$171.15	$171.20
Purchase #5	$147.78	13.859%	$168.2608	$168.26	$168.25	$168.30
Purchase #6	$67.37	4.552%	$70.4367	$70.44	$70.45	$70.40
Purchase #7	$90.82	5.747%	$96.0394	$96.04	$96.05	$96.00
7 purchase totals =	$652.75		$710.0528	$710.05	$710.05	$710.00