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	$109.38	4.561%	$114.3688	$114.37	$114.35	$114.40
Purchase #2	$154.46	3.376%	$159.6746	$159.67	$159.65	$159.70
Purchase #3	$235.45	6.524%	$250.8108	$250.81	$250.80	$250.80
Purchase #4	$153.48	12.250%	$172.2813	$172.28	$172.30	$172.30
Purchase #5	$127.40	4.231%	$132.7903	$132.79	$132.80	$132.80
Purchase #6	$92.52	4.198%	$96.404	$96.40	$96.40	$96.40
Purchase #7	$96.29	9.279%	$105.2247	$105.22	$105.20	$105.20
7 purchase totals =	$968.98		$1,031.5545	$1,031.54	$1,031.50	$1,031.60