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	$236.26	11.809%	$264.1599	$264.16	$264.15	$264.20
Purchase #2	$23.53	4.787%	$24.6564	$24.66	$24.65	$24.70
Purchase #3	$163.86	13.107%	$185.3371	$185.34	$185.35	$185.30
Purchase #4	$182.90	8.570%	$198.5745	$198.57	$198.55	$198.60
Purchase #5	$184.55	6.439%	$196.4332	$196.43	$196.45	$196.40
Purchase #6	$231.32	4.106%	$240.818	$240.82	$240.80	$240.80
Purchase #7	$32.77	8.794%	$35.6518	$35.65	$35.65	$35.70
7 purchase totals =	$1,055.19		$1,145.6309	$1,145.63	$1,145.60	$1,145.70