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	$161.61	4.351%	$168.6417	$168.64	$168.65	$168.60
Purchase #2	$79.86	10.406%	$88.1702	$88.17	$88.15	$88.20
Purchase #3	$116.90	9.727%	$128.2709	$128.27	$128.25	$128.30
Purchase #4	$64.64	10.679%	$71.5429	$71.54	$71.55	$71.50
Purchase #5	$37.75	11.491%	$42.0879	$42.09	$42.10	$42.10
Purchase #6	$226.85	13.611%	$257.7266	$257.73	$257.75	$257.70
Purchase #7	$200.98	6.141%	$213.3222	$213.32	$213.30	$213.30
7 purchase totals =	$888.59		$969.7624	$969.76	$969.75	$969.70