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	$133.69	9.420%	$146.2836	$146.28	$146.30	$146.30
Purchase #2	$212.51	9.123%	$231.8973	$231.90	$231.90	$231.90
Purchase #3	$50.91	3.691%	$52.7891	$52.79	$52.80	$52.80
Purchase #4	$51.63	9.313%	$56.4383	$56.44	$56.45	$56.40
Purchase #5	$242.80	12.803%	$273.8857	$273.89	$273.90	$273.90
Purchase #6	$151.89	4.709%	$159.0425	$159.04	$159.05	$159.00
Purchase #7	$207.67	7.719%	$223.7	$223.70	$223.70	$223.70
7 purchase totals =	$1,051.10		$1,144.0365	$1,144.04	$1,144.10	$1,144.00