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	$169.39	7.400%	$181.9249	$181.92	$181.90	$181.90
Purchase #2	$119.88	11.765%	$133.9839	$133.98	$134.00	$134.00
Purchase #3	$77.34	3.825%	$80.2983	$80.30	$80.30	$80.30
Purchase #4	$18.46	12.862%	$20.8343	$20.83	$20.85	$20.80
Purchase #5	$216.72	7.111%	$232.131	$232.13	$232.15	$232.10
Purchase #6	$201.83	12.769%	$227.6017	$227.60	$227.60	$227.60
Purchase #7	$72.34	13.476%	$82.0885	$82.09	$82.10	$82.10
7 purchase totals =	$875.96		$958.8626	$958.85	$958.90	$958.80