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	$131.99	6.841%	$141.0194	$141.02	$141.00	$141.00
Purchase #2	$35.71	9.409%	$39.07	$39.07	$39.05	$39.10
Purchase #3	$92.68	9.751%	$101.7172	$101.72	$101.70	$101.70
Purchase #4	$82.37	10.276%	$90.8343	$90.83	$90.85	$90.80
Purchase #5	$170.60	11.501%	$190.2207	$190.22	$190.20	$190.20
Purchase #6	$136.85	4.163%	$142.5471	$142.55	$142.55	$142.50
Purchase #7	$43.64	10.524%	$48.2327	$48.23	$48.25	$48.20
7 purchase totals =	$693.84		$753.6414	$753.64	$753.60	$753.50