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	$161.52	6.466%	$171.9639	$171.96	$171.95	$172.00
Purchase #2	$135.78	7.852%	$146.4414	$146.44	$146.45	$146.40
Purchase #3	$116.71	5.647%	$123.3006	$123.30	$123.30	$123.30
Purchase #4	$178.56	11.787%	$199.6069	$199.61	$199.60	$199.60
Purchase #5	$53.38	6.512%	$56.8561	$56.86	$56.85	$56.90
Purchase #6	$174.41	9.656%	$191.251	$191.25	$191.25	$191.30
Purchase #7	$61.86	4.724%	$64.7823	$64.78	$64.80	$64.80
7 purchase totals =	$882.22		$954.2022	$954.20	$954.20	$954.30