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	$178.59	6.588%	$190.3555	$190.36	$190.35	$190.40
Purchase #2	$136.84	11.641%	$152.7695	$152.77	$152.75	$152.80
Purchase #3	$99.97	11.300%	$111.2666	$111.27	$111.25	$111.30
Purchase #4	$239.29	6.684%	$255.2841	$255.28	$255.30	$255.30
Purchase #5	$96.81	4.548%	$101.2129	$101.21	$101.20	$101.20
Purchase #6	$103.70	11.699%	$115.8319	$115.83	$115.85	$115.80
Purchase #7	$120.56	5.159%	$126.7797	$126.78	$126.80	$126.80
7 purchase totals =	$975.76		$1,053.5002	$1,053.50	$1,053.50	$1,053.60