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	$170.77	11.317%	$190.096	$190.10	$190.10	$190.10
Purchase #2	$106.59	9.801%	$117.0369	$117.04	$117.05	$117.00
Purchase #3	$146.76	3.847%	$152.4059	$152.41	$152.40	$152.40
Purchase #4	$93.31	12.570%	$105.0391	$105.04	$105.05	$105.00
Purchase #5	$203.86	3.128%	$210.2367	$210.24	$210.25	$210.20
Purchase #6	$85.82	13.208%	$97.1551	$97.16	$97.15	$97.20
Purchase #7	$160.81	10.662%	$177.9556	$177.96	$177.95	$178.00
7 purchase totals =	$967.92		$1,049.9253	$1,049.95	$1,049.95	$1,049.90