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	$81.31	13.109%	$91.9689	$91.97	$91.95	$92.00
Purchase #2	$140.64	10.844%	$155.891	$155.89	$155.90	$155.90
Purchase #3	$104.82	8.617%	$113.8523	$113.85	$113.85	$113.90
Purchase #4	$165.50	3.804%	$171.7956	$171.80	$171.80	$171.80
Purchase #5	$199.48	10.818%	$221.0597	$221.06	$221.05	$221.10
Purchase #6	$175.51	8.142%	$189.8	$189.80	$189.80	$189.80
Purchase #7	$95.35	5.498%	$100.5923	$100.59	$100.60	$100.60
7 purchase totals =	$962.61		$1,044.9598	$1,044.96	$1,044.95	$1,045.10