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	$147.29	11.547%	$164.2976	$164.30	$164.30	$164.30
Purchase #2	$136.59	3.784%	$141.7586	$141.76	$141.75	$141.80
Purchase #3	$69.46	9.811%	$76.2747	$76.27	$76.25	$76.30
Purchase #4	$58.72	12.215%	$65.8926	$65.89	$65.90	$65.90
Purchase #5	$54.52	12.321%	$61.2374	$61.24	$61.25	$61.20
Purchase #6	$106.30	13.674%	$120.8355	$120.84	$120.85	$120.80
Purchase #7	$210.74	5.279%	$221.865	$221.87	$221.85	$221.90
7 purchase totals =	$783.62		$852.1614	$852.17	$852.15	$852.20