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	$58.63	5.308%	$61.7421	$61.74	$61.75	$61.70
Purchase #2	$186.56	13.793%	$212.2922	$212.29	$212.30	$212.30
Purchase #3	$101.29	9.623%	$111.0371	$111.04	$111.05	$111.00
Purchase #4	$95.41	4.227%	$99.443	$99.44	$99.45	$99.40
Purchase #5	$35.65	4.736%	$37.3384	$37.34	$37.35	$37.30
Purchase #6	$72.74	10.225%	$80.1777	$80.18	$80.20	$80.20
Purchase #7	$81.28	5.512%	$85.7602	$85.76	$85.75	$85.80
7 purchase totals =	$631.56		$687.7907	$687.79	$687.85	$687.70