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	$191.94	7.642%	$206.6081	$206.61	$206.60	$206.60
Purchase #2	$33.72	10.205%	$37.1611	$37.16	$37.15	$37.20
Purchase #3	$81.81	12.275%	$91.8522	$91.85	$91.85	$91.90
Purchase #4	$165.56	7.688%	$178.2883	$178.29	$178.30	$178.30
Purchase #5	$247.31	9.505%	$270.8168	$270.82	$270.80	$270.80
Purchase #6	$56.85	3.806%	$59.0137	$59.01	$59.00	$59.00
Purchase #7	$28.85	9.842%	$31.6894	$31.69	$31.70	$31.70
7 purchase totals =	$806.04		$875.4296	$875.43	$875.40	$875.50