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	$145.61	13.113%	$164.7038	$164.70	$164.70	$164.70
Purchase #2	$163.49	6.454%	$174.0416	$174.04	$174.05	$174.00
Purchase #3	$230.97	3.301%	$238.5943	$238.59	$238.60	$238.60
Purchase #4	$123.47	6.795%	$131.8598	$131.86	$131.85	$131.90
Purchase #5	$102.87	8.215%	$111.3208	$111.32	$111.30	$111.30
Purchase #6	$54.79	4.117%	$57.0457	$57.05	$57.05	$57.00
Purchase #7	$82.74	10.830%	$91.7007	$91.70	$91.70	$91.70
7 purchase totals =	$903.94		$969.2667	$969.26	$969.25	$969.20