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	$162.93	13.751%	$185.3345	$185.33	$185.35	$185.30
Purchase #2	$39.65	6.623%	$42.276	$42.28	$42.30	$42.30
Purchase #3	$79.69	7.696%	$85.8229	$85.82	$85.80	$85.80
Purchase #4	$87.70	8.437%	$95.0992	$95.10	$95.10	$95.10
Purchase #5	$192.82	10.763%	$213.5732	$213.57	$213.55	$213.60
Purchase #6	$82.63	10.384%	$91.2103	$91.21	$91.20	$91.20
Purchase #7	$130.53	8.654%	$141.8261	$141.83	$141.85	$141.80
7 purchase totals =	$775.95		$855.1422	$855.14	$855.15	$855.10