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	$86.25	3.294%	$89.0911	$89.09	$89.10	$89.10
Purchase #2	$221.64	11.826%	$247.8511	$247.85	$247.85	$247.90
Purchase #3	$85.75	11.157%	$95.3171	$95.32	$95.30	$95.30
Purchase #4	$184.97	8.695%	$201.0531	$201.05	$201.05	$201.10
Purchase #5	$136.71	11.556%	$152.5082	$152.51	$152.50	$152.50
Purchase #6	$77.68	3.640%	$80.5076	$80.51	$80.50	$80.50
Purchase #7	$161.83	7.554%	$174.0546	$174.05	$174.05	$174.10
7 purchase totals =	$954.83		$1,040.3828	$1,040.38	$1,040.35	$1,040.50