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	$185.82	11.129%	$206.4999	$206.50	$206.50	$206.50
Purchase #2	$53.29	3.494%	$55.152	$55.15	$55.15	$55.20
Purchase #3	$140.62	4.459%	$146.8902	$146.89	$146.90	$146.90
Purchase #4	$250.80	9.490%	$274.6009	$274.60	$274.60	$274.60
Purchase #5	$242.39	7.693%	$261.0371	$261.04	$261.05	$261.00
Purchase #6	$35.40	6.216%	$37.6005	$37.60	$37.60	$37.60
Purchase #7	$143.99	12.855%	$162.4999	$162.50	$162.50	$162.50
7 purchase totals =	$1,052.31		$1,144.2805	$1,144.28	$1,144.30	$1,144.30