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	$221.28	4.185%	$230.5406	$230.54	$230.55	$230.50
Purchase #2	$79.91	10.342%	$88.1743	$88.17	$88.15	$88.20
Purchase #3	$199.28	4.327%	$207.9028	$207.90	$207.90	$207.90
Purchase #4	$96.77	9.148%	$105.6225	$105.62	$105.60	$105.60
Purchase #5	$224.93	13.270%	$254.7782	$254.78	$254.80	$254.80
Purchase #6	$161.39	4.396%	$168.4847	$168.48	$168.50	$168.50
Purchase #7	$27.40	6.212%	$29.1021	$29.10	$29.10	$29.10
7 purchase totals =	$1,010.96		$1,084.6052	$1,084.59	$1,084.60	$1,084.60