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	$178.92	6.757%	$191.0096	$191.01	$191.00	$191.00
Purchase #2	$169.53	9.347%	$185.376	$185.38	$185.40	$185.40
Purchase #3	$57.29	12.385%	$64.3854	$64.39	$64.40	$64.40
Purchase #4	$150.50	13.789%	$171.2524	$171.25	$171.25	$171.30
Purchase #5	$189.50	12.669%	$213.5078	$213.51	$213.50	$213.50
Purchase #6	$59.67	13.396%	$67.6634	$67.66	$67.65	$67.70
Purchase #7	$111.99	10.756%	$124.0356	$124.04	$124.05	$124.00
7 purchase totals =	$917.40		$1,017.2302	$1,017.24	$1,017.25	$1,017.30