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	$67.95	3.403%	$70.2623	$70.26	$70.25	$70.30
Purchase #2	$168.62	13.406%	$191.2252	$191.23	$191.25	$191.20
Purchase #3	$195.78	4.372%	$204.3395	$204.34	$204.35	$204.30
Purchase #4	$89.82	13.128%	$101.6116	$101.61	$101.60	$101.60
Purchase #5	$73.66	8.844%	$80.1745	$80.17	$80.15	$80.20
Purchase #6	$64.50	12.467%	$72.5412	$72.54	$72.55	$72.50
Purchase #7	$40.91	12.406%	$45.9853	$45.99	$46.00	$46.00
7 purchase totals =	$701.24		$766.1396	$766.14	$766.15	$766.10