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	$195.25	5.293%	$205.5846	$205.58	$205.60	$205.60
Purchase #2	$92.82	6.801%	$99.1327	$99.13	$99.15	$99.10
Purchase #3	$47.77	7.356%	$51.284	$51.28	$51.30	$51.30
Purchase #4	$56.85	8.277%	$61.5555	$61.56	$61.55	$61.60
Purchase #5	$28.33	6.817%	$30.2613	$30.26	$30.25	$30.30
Purchase #6	$97.52	8.503%	$105.8121	$105.81	$105.80	$105.80
Purchase #7	$221.67	12.682%	$249.7822	$249.78	$249.80	$249.80
7 purchase totals =	$740.21		$803.4124	$803.40	$803.45	$803.50