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	$247.44	4.781%	$259.2701	$259.27	$259.25	$259.30
Purchase #2	$112.68	3.489%	$116.6114	$116.61	$116.60	$116.60
Purchase #3	$133.26	6.227%	$141.5581	$141.56	$141.55	$141.60
Purchase #4	$82.53	11.496%	$92.0176	$92.02	$92.00	$92.00
Purchase #5	$160.45	7.219%	$172.0329	$172.03	$172.05	$172.00
Purchase #6	$116.74	11.836%	$130.5573	$130.56	$130.55	$130.60
Purchase #7	$91.63	12.618%	$103.1919	$103.19	$103.20	$103.20
7 purchase totals =	$944.73		$1,015.2393	$1,015.24	$1,015.20	$1,015.30