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	$89.87	11.128%	$99.8707	$99.87	$99.85	$99.90
Purchase #2	$109.45	6.267%	$116.3092	$116.31	$116.30	$116.30
Purchase #3	$149.75	4.825%	$156.9754	$156.98	$157.00	$157.00
Purchase #4	$89.63	6.403%	$95.369	$95.37	$95.35	$95.40
Purchase #5	$204.31	7.337%	$219.3002	$219.30	$219.30	$219.30
Purchase #6	$139.64	10.389%	$154.1472	$154.15	$154.15	$154.10
Purchase #7	$91.26	9.335%	$99.7791	$99.78	$99.80	$99.80
7 purchase totals =	$873.91		$941.7508	$941.76	$941.75	$941.80