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	$139.78	4.709%	$146.3622	$146.36	$146.35	$146.40
Purchase #2	$126.70	13.136%	$143.3433	$143.34	$143.35	$143.30
Purchase #3	$183.71	6.747%	$196.1049	$196.10	$196.10	$196.10
Purchase #4	$157.37	3.154%	$162.3334	$162.33	$162.35	$162.30
Purchase #5	$111.81	7.481%	$120.1745	$120.17	$120.15	$120.20
Purchase #6	$24.86	7.192%	$26.6479	$26.65	$26.65	$26.60
Purchase #7	$232.61	13.443%	$263.8798	$263.88	$263.90	$263.90
7 purchase totals =	$976.84		$1,058.8460	$1,058.83	$1,058.85	$1,058.80