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	$99.67	10.705%	$110.3397	$110.34	$110.35	$110.30
Purchase #2	$216.99	9.759%	$238.1661	$238.17	$238.15	$238.20
Purchase #3	$158.98	6.627%	$169.5156	$169.52	$169.50	$169.50
Purchase #4	$162.47	4.873%	$170.3872	$170.39	$170.40	$170.40
Purchase #5	$174.87	10.229%	$192.7575	$192.76	$192.75	$192.80
Purchase #6	$132.45	13.364%	$150.1506	$150.15	$150.15	$150.20
Purchase #7	$57.27	9.743%	$62.8498	$62.85	$62.85	$62.80
7 purchase totals =	$1,002.70		$1,094.1665	$1,094.18	$1,094.15	$1,094.20