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	$207.73	4.421%	$216.9137	$216.91	$216.90	$216.90
Purchase #2	$228.87	6.224%	$243.1149	$243.11	$243.10	$243.10
Purchase #3	$74.28	8.224%	$80.3888	$80.39	$80.40	$80.40
Purchase #4	$128.41	8.699%	$139.5804	$139.58	$139.60	$139.60
Purchase #5	$111.90	10.261%	$123.3821	$123.38	$123.40	$123.40
Purchase #6	$44.89	11.180%	$49.9087	$49.91	$49.90	$49.90
Purchase #7	$212.78	7.408%	$228.5427	$228.54	$228.55	$228.50
7 purchase totals =	$1,008.86		$1,081.8313	$1,081.82	$1,081.85	$1,081.80