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	$152.74	3.330%	$157.8262	$157.83	$157.85	$157.80
Purchase #2	$156.83	3.566%	$162.4226	$162.42	$162.40	$162.40
Purchase #3	$151.82	11.244%	$168.8906	$168.89	$168.90	$168.90
Purchase #4	$29.90	11.460%	$33.3265	$33.33	$33.35	$33.30
Purchase #5	$168.71	3.592%	$174.7701	$174.77	$174.75	$174.80
Purchase #6	$98.54	3.123%	$101.6174	$101.62	$101.60	$101.60
Purchase #7	$157.78	11.619%	$176.1125	$176.11	$176.10	$176.10
7 purchase totals =	$916.32		$974.9659	$974.97	$974.95	$974.90