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	$32.35	3.413%	$33.4541	$33.45	$33.45	$33.50
Purchase #2	$77.91	3.696%	$80.7896	$80.79	$80.80	$80.80
Purchase #3	$139.33	9.455%	$152.5037	$152.50	$152.50	$152.50
Purchase #4	$7.71	11.196%	$8.5732	$8.57	$8.55	$8.60
Purchase #5	$77.76	10.442%	$85.8797	$85.88	$85.90	$85.90
Purchase #6	$171.35	9.745%	$188.0481	$188.05	$188.05	$188.00
Purchase #7	$9.67	7.325%	$10.3783	$10.38	$10.40	$10.40
7 purchase totals =	$516.08		$559.6267	$559.62	$559.65	$559.70