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	$232.31	9.290%	$253.8916	$253.89	$253.90	$253.90
Purchase #2	$168.62	8.395%	$182.7756	$182.78	$182.80	$182.80
Purchase #3	$139.86	4.787%	$146.5551	$146.56	$146.55	$146.60
Purchase #4	$148.61	11.667%	$165.9483	$165.95	$165.95	$165.90
Purchase #5	$157.97	11.303%	$175.8253	$175.83	$175.85	$175.80
Purchase #6	$147.35	3.432%	$152.4071	$152.41	$152.40	$152.40
Purchase #7	$156.81	4.778%	$164.3024	$164.30	$164.30	$164.30
7 purchase totals =	$1,151.53		$1,241.7054	$1,241.72	$1,241.75	$1,241.70