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	$148.64	6.368%	$158.1054	$158.11	$158.10	$158.10
Purchase #2	$104.63	13.573%	$118.8314	$118.83	$118.85	$118.80
Purchase #3	$61.44	6.239%	$65.2732	$65.27	$65.25	$65.30
Purchase #4	$121.91	7.843%	$131.4714	$131.47	$131.45	$131.50
Purchase #5	$141.41	3.630%	$146.5432	$146.54	$146.55	$146.50
Purchase #6	$219.61	12.393%	$246.8263	$246.83	$246.85	$246.80
Purchase #7	$18.85	7.777%	$20.316	$20.32	$20.30	$20.30
7 purchase totals =	$816.49		$887.3669	$887.37	$887.35	$887.30