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	$104.33	3.517%	$107.9993	$108.00	$108.00	$108.00
Purchase #2	$109.59	6.503%	$116.7166	$116.72	$116.70	$116.70
Purchase #3	$36.29	6.443%	$38.6282	$38.63	$38.65	$38.60
Purchase #4	$189.71	3.324%	$196.016	$196.02	$196.00	$196.00
Purchase #5	$37.82	10.778%	$41.8962	$41.90	$41.90	$41.90
Purchase #6	$207.56	3.465%	$214.752	$214.75	$214.75	$214.80
Purchase #7	$31.56	12.527%	$35.5135	$35.51	$35.50	$35.50
7 purchase totals =	$716.86		$751.5218	$751.53	$751.50	$751.50