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	$70.56	11.383%	$78.5918	$78.59	$78.60	$78.60
Purchase #2	$111.67	13.135%	$126.3379	$126.34	$126.35	$126.30
Purchase #3	$9.88	9.190%	$10.788	$10.79	$10.80	$10.80
Purchase #4	$35.30	6.456%	$37.579	$37.58	$37.60	$37.60
Purchase #5	$166.39	13.673%	$189.1405	$189.14	$189.15	$189.10
Purchase #6	$141.65	7.424%	$152.1661	$152.17	$152.15	$152.20
Purchase #7	$104.34	3.843%	$108.3498	$108.35	$108.35	$108.30
7 purchase totals =	$639.79		$702.9531	$702.96	$703.00	$702.90