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	$36.57	3.298%	$37.7761	$37.78	$37.80	$37.80
Purchase #2	$174.45	13.670%	$198.2973	$198.30	$198.30	$198.30
Purchase #3	$127.85	4.700%	$133.859	$133.86	$133.85	$133.90
Purchase #4	$218.38	12.462%	$245.5945	$245.59	$245.60	$245.60
Purchase #5	$50.72	12.782%	$57.203	$57.20	$57.20	$57.20
Purchase #6	$152.28	10.143%	$167.7258	$167.73	$167.75	$167.70
Purchase #7	$161.93	5.637%	$171.058	$171.06	$171.05	$171.10
7 purchase totals =	$922.18		$1,011.5137	$1,011.52	$1,011.55	$1,011.60