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	$158.56	4.736%	$166.0694	$166.07	$166.05	$166.10
Purchase #2	$83.87	11.234%	$93.292	$93.29	$93.30	$93.30
Purchase #3	$136.29	4.311%	$142.1655	$142.17	$142.15	$142.20
Purchase #4	$221.30	12.253%	$248.4159	$248.42	$248.40	$248.40
Purchase #5	$153.37	3.515%	$158.761	$158.76	$158.75	$158.80
Purchase #6	$91.64	13.838%	$104.3211	$104.32	$104.30	$104.30
Purchase #7	$42.70	7.478%	$45.8931	$45.89	$45.90	$45.90
7 purchase totals =	$887.73		$958.9180	$958.92	$958.85	$959.00