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	$197.38	3.768%	$204.8173	$204.82	$204.80	$204.80
Purchase #2	$57.31	3.771%	$59.4712	$59.47	$59.45	$59.50
Purchase #3	$137.56	9.173%	$150.1784	$150.18	$150.20	$150.20
Purchase #4	$240.87	5.460%	$254.0215	$254.02	$254.00	$254.00
Purchase #5	$111.58	4.799%	$116.9347	$116.93	$116.95	$116.90
Purchase #6	$158.65	7.806%	$171.0342	$171.03	$171.05	$171.00
Purchase #7	$104.97	4.523%	$109.7178	$109.72	$109.70	$109.70
7 purchase totals =	$1,008.32		$1,066.1751	$1,066.17	$1,066.15	$1,066.10