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	$91.86	4.115%	$95.64	$95.64	$95.65	$95.60
Purchase #2	$55.66	7.209%	$59.6725	$59.67	$59.65	$59.70
Purchase #3	$244.43	12.190%	$274.226	$274.23	$274.25	$274.20
Purchase #4	$171.33	11.676%	$191.3345	$191.33	$191.35	$191.30
Purchase #5	$57.89	3.424%	$59.8722	$59.87	$59.85	$59.90
Purchase #6	$149.90	6.417%	$159.5191	$159.52	$159.50	$159.50
Purchase #7	$92.89	9.550%	$101.761	$101.76	$101.75	$101.80
7 purchase totals =	$863.96		$942.0253	$942.02	$942.00	$942.00