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	$231.91	11.180%	$257.8375	$257.84	$257.85	$257.80
Purchase #2	$246.84	9.228%	$269.6184	$269.62	$269.60	$269.60
Purchase #3	$96.36	4.134%	$100.3435	$100.34	$100.35	$100.30
Purchase #4	$81.28	10.591%	$89.8884	$89.89	$89.90	$89.90
Purchase #5	$6.48	7.732%	$6.981	$6.98	$7.00	$7.00
Purchase #6	$230.47	10.491%	$254.6486	$254.65	$254.65	$254.60
Purchase #7	$130.95	13.530%	$148.6675	$148.67	$148.65	$148.70
7 purchase totals =	$1,024.29		$1,127.9849	$1,127.99	$1,128.00	$1,127.90