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	$76.52	9.183%	$83.5468	$83.55	$83.55	$83.50
Purchase #2	$54.65	8.481%	$59.2849	$59.28	$59.30	$59.30
Purchase #3	$97.47	5.770%	$103.094	$103.09	$103.10	$103.10
Purchase #4	$135.35	9.132%	$147.7102	$147.71	$147.70	$147.70
Purchase #5	$219.72	6.358%	$233.6898	$233.69	$233.70	$233.70
Purchase #6	$134.91	4.630%	$141.1563	$141.16	$141.15	$141.20
Purchase #7	$87.99	9.429%	$96.2866	$96.29	$96.30	$96.30
7 purchase totals =	$806.61		$864.7686	$864.77	$864.80	$864.80