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	$194.85	9.823%	$213.9901	$213.99	$214.00	$214.00
Purchase #2	$41.30	9.645%	$45.2834	$45.28	$45.30	$45.30
Purchase #3	$85.42	6.322%	$90.8203	$90.82	$90.80	$90.80
Purchase #4	$19.72	6.621%	$21.0257	$21.03	$21.05	$21.00
Purchase #5	$76.55	3.382%	$79.1389	$79.14	$79.15	$79.10
Purchase #6	$81.42	11.791%	$91.0202	$91.02	$91.00	$91.00
Purchase #7	$92.33	3.201%	$95.2855	$95.29	$95.30	$95.30
7 purchase totals =	$591.59		$636.5641	$636.57	$636.60	$636.50