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	$227.90	4.714%	$238.6432	$238.64	$238.65	$238.60
Purchase #2	$234.59	10.760%	$259.8319	$259.83	$259.85	$259.80
Purchase #3	$77.99	3.596%	$80.7945	$80.79	$80.80	$80.80
Purchase #4	$96.37	8.837%	$104.8862	$104.89	$104.90	$104.90
Purchase #5	$227.59	6.138%	$241.5595	$241.56	$241.55	$241.60
Purchase #6	$245.67	8.803%	$267.2963	$267.30	$267.30	$267.30
Purchase #7	$38.39	10.696%	$42.4962	$42.50	$42.50	$42.50
7 purchase totals =	$1,148.50		$1,235.5078	$1,235.51	$1,235.55	$1,235.50