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	$125.59	3.825%	$130.3938	$130.39	$130.40	$130.40
Purchase #2	$177.68	7.620%	$191.2192	$191.22	$191.20	$191.20
Purchase #3	$110.26	11.469%	$122.9057	$122.91	$122.90	$122.90
Purchase #4	$225.83	7.197%	$242.083	$242.08	$242.10	$242.10
Purchase #5	$161.54	4.547%	$168.8852	$168.89	$168.90	$168.90
Purchase #6	$64.90	4.511%	$67.8276	$67.83	$67.85	$67.80
Purchase #7	$135.92	4.798%	$142.4414	$142.44	$142.45	$142.40
7 purchase totals =	$1,001.72		$1,065.7559	$1,065.76	$1,065.80	$1,065.70