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	$104.42	7.523%	$112.2755	$112.28	$112.30	$112.30
Purchase #2	$9.90	3.722%	$10.2685	$10.27	$10.25	$10.30
Purchase #3	$97.38	12.845%	$109.8885	$109.89	$109.90	$109.90
Purchase #4	$141.34	6.623%	$150.7009	$150.70	$150.70	$150.70
Purchase #5	$109.35	4.665%	$114.4512	$114.45	$114.45	$114.50
Purchase #6	$130.45	4.396%	$136.1846	$136.18	$136.20	$136.20
Purchase #7	$159.58	3.570%	$165.277	$165.28	$165.30	$165.30
7 purchase totals =	$752.42		$799.0462	$799.05	$799.10	$799.20