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	$111.61	4.438%	$116.5633	$116.56	$116.55	$116.60
Purchase #2	$79.34	13.237%	$89.8422	$89.84	$89.85	$89.80
Purchase #3	$46.98	8.388%	$50.9207	$50.92	$50.90	$50.90
Purchase #4	$110.92	8.309%	$120.1363	$120.14	$120.15	$120.10
Purchase #5	$158.40	3.714%	$164.283	$164.28	$164.30	$164.30
Purchase #6	$115.89	7.850%	$124.9874	$124.99	$125.00	$125.00
Purchase #7	$127.25	11.518%	$141.9067	$141.91	$141.90	$141.90
7 purchase totals =	$750.39		$808.6396	$808.64	$808.65	$808.60