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	$130.68	7.870%	$140.9645	$140.96	$140.95	$141.00
Purchase #2	$147.30	12.201%	$165.2721	$165.27	$165.25	$165.30
Purchase #3	$104.71	6.813%	$111.8439	$111.84	$111.85	$111.80
Purchase #4	$123.83	7.442%	$133.0454	$133.05	$133.05	$133.00
Purchase #5	$126.71	10.764%	$140.3491	$140.35	$140.35	$140.30
Purchase #6	$31.37	6.177%	$33.3077	$33.31	$33.30	$33.30
Purchase #7	$25.68	12.248%	$28.8253	$28.83	$28.85	$28.80
7 purchase totals =	$690.28		$753.6080	$753.61	$753.60	$753.50