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	$62.98	13.217%	$71.3041	$71.30	$71.30	$71.30
Purchase #2	$205.64	7.459%	$220.9787	$220.98	$221.00	$221.00
Purchase #3	$32.83	8.543%	$35.6347	$35.63	$35.65	$35.60
Purchase #4	$37.82	12.674%	$42.6133	$42.61	$42.60	$42.60
Purchase #5	$79.95	10.236%	$88.1337	$88.13	$88.15	$88.10
Purchase #6	$100.93	12.719%	$113.7673	$113.77	$113.75	$113.80
Purchase #7	$48.97	8.513%	$53.1388	$53.14	$53.15	$53.10
7 purchase totals =	$569.12		$625.5706	$625.56	$625.60	$625.50