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	$209.56	4.150%	$218.2567	$218.26	$218.25	$218.30
Purchase #2	$164.61	6.861%	$175.9039	$175.90	$175.90	$175.90
Purchase #3	$106.81	9.207%	$116.644	$116.64	$116.65	$116.60
Purchase #4	$71.40	11.297%	$79.4661	$79.47	$79.45	$79.50
Purchase #5	$116.98	9.201%	$127.7433	$127.74	$127.75	$127.70
Purchase #6	$46.48	7.674%	$50.0469	$50.05	$50.05	$50.00
Purchase #7	$48.75	11.413%	$54.3138	$54.31	$54.30	$54.30
7 purchase totals =	$764.59		$822.3747	$822.37	$822.35	$822.30