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	$223.48	8.685%	$242.8892	$242.89	$242.90	$242.90
Purchase #2	$84.57	11.472%	$94.2719	$94.27	$94.25	$94.30
Purchase #3	$141.59	10.718%	$156.7656	$156.77	$156.75	$156.80
Purchase #4	$124.83	4.488%	$130.4324	$130.43	$130.45	$130.40
Purchase #5	$128.68	10.377%	$142.0331	$142.03	$142.05	$142.00
Purchase #6	$204.29	7.155%	$218.9069	$218.91	$218.90	$218.90
Purchase #7	$220.80	7.608%	$237.5985	$237.60	$237.60	$237.60
7 purchase totals =	$1,128.24		$1,222.8976	$1,222.90	$1,222.90	$1,222.90