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	$169.51	9.641%	$185.8525	$185.85	$185.85	$185.90
Purchase #2	$141.64	7.229%	$151.8792	$151.88	$151.90	$151.90
Purchase #3	$114.59	8.746%	$124.612	$124.61	$124.60	$124.60
Purchase #4	$159.71	7.415%	$171.5525	$171.55	$171.55	$171.60
Purchase #5	$135.69	4.251%	$141.4582	$141.46	$141.45	$141.50
Purchase #6	$49.44	4.489%	$51.6594	$51.66	$51.65	$51.70
Purchase #7	$157.40	7.858%	$169.7685	$169.77	$169.75	$169.80
7 purchase totals =	$927.98		$996.7823	$996.78	$996.75	$997.00