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	$239.78	5.401%	$252.7305	$252.73	$252.75	$252.70
Purchase #2	$151.59	11.511%	$169.0395	$169.04	$169.05	$169.00
Purchase #3	$112.73	5.385%	$118.8005	$118.80	$118.80	$118.80
Purchase #4	$86.64	9.788%	$95.1203	$95.12	$95.10	$95.10
Purchase #5	$198.94	6.627%	$212.1238	$212.12	$212.10	$212.10
Purchase #6	$72.92	13.574%	$82.8182	$82.82	$82.80	$82.80
Purchase #7	$82.62	5.168%	$86.8898	$86.89	$86.90	$86.90
7 purchase totals =	$945.22		$1,017.5226	$1,017.52	$1,017.50	$1,017.40