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	$95.57	3.343%	$98.7649	$98.76	$98.75	$98.80
Purchase #2	$216.98	4.872%	$227.5513	$227.55	$227.55	$227.60
Purchase #3	$89.71	12.133%	$100.5945	$100.59	$100.60	$100.60
Purchase #4	$128.75	6.559%	$137.1947	$137.19	$137.20	$137.20
Purchase #5	$50.92	12.636%	$57.3543	$57.35	$57.35	$57.40
Purchase #6	$168.91	9.722%	$185.3314	$185.33	$185.35	$185.30
Purchase #7	$103.83	8.771%	$112.9369	$112.94	$112.95	$112.90
7 purchase totals =	$854.67		$919.7280	$919.71	$919.75	$919.80