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	$215.98	6.347%	$229.6883	$229.69	$229.70	$229.70
Purchase #2	$169.88	12.513%	$191.1371	$191.14	$191.15	$191.10
Purchase #3	$157.45	11.541%	$175.6213	$175.62	$175.60	$175.60
Purchase #4	$43.74	11.696%	$48.8558	$48.86	$48.85	$48.90
Purchase #5	$81.62	11.390%	$90.9165	$90.92	$90.90	$90.90
Purchase #6	$85.62	7.356%	$91.9182	$91.92	$91.90	$91.90
Purchase #7	$13.60	7.422%	$14.6094	$14.61	$14.60	$14.60
7 purchase totals =	$767.89		$842.7466	$842.76	$842.70	$842.70