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	$100.40	12.519%	$112.9691	$112.97	$112.95	$113.00
Purchase #2	$17.28	13.222%	$19.5648	$19.56	$19.55	$19.60
Purchase #3	$13.87	13.325%	$15.7182	$15.72	$15.70	$15.70
Purchase #4	$184.96	3.317%	$191.0951	$191.10	$191.10	$191.10
Purchase #5	$172.90	13.670%	$196.5354	$196.54	$196.55	$196.50
Purchase #6	$234.76	9.453%	$256.9519	$256.95	$256.95	$257.00
Purchase #7	$59.89	3.596%	$62.0436	$62.04	$62.05	$62.00
7 purchase totals =	$784.06		$854.8781	$854.88	$854.85	$854.90