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	$128.84	10.132%	$141.8941	$141.89	$141.90	$141.90
Purchase #2	$144.97	8.340%	$157.0605	$157.06	$157.05	$157.10
Purchase #3	$44.70	10.436%	$49.3649	$49.36	$49.35	$49.40
Purchase #4	$84.88	13.786%	$96.5816	$96.58	$96.60	$96.60
Purchase #5	$51.87	11.641%	$57.9082	$57.91	$57.90	$57.90
Purchase #6	$182.58	7.683%	$196.6076	$196.61	$196.60	$196.60
Purchase #7	$25.89	11.583%	$28.8888	$28.89	$28.90	$28.90
7 purchase totals =	$663.73		$728.3057	$728.30	$728.30	$728.40