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	$156.56	11.310%	$174.2669	$174.27	$174.25	$174.30
Purchase #2	$34.25	7.413%	$36.789	$36.79	$36.80	$36.80
Purchase #3	$175.87	11.794%	$196.6121	$196.61	$196.60	$196.60
Purchase #4	$10.45	8.387%	$11.3264	$11.33	$11.35	$11.30
Purchase #5	$196.28	8.238%	$212.4495	$212.45	$212.45	$212.40
Purchase #6	$10.87	8.564%	$11.8009	$11.80	$11.80	$11.80
Purchase #7	$229.50	10.465%	$253.5172	$253.52	$253.50	$253.50
7 purchase totals =	$813.78		$896.7620	$896.77	$896.75	$896.70