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	$176.27	8.398%	$191.0732	$191.07	$191.05	$191.10
Purchase #2	$111.59	4.737%	$116.876	$116.88	$116.90	$116.90
Purchase #3	$160.73	12.250%	$180.4194	$180.42	$180.40	$180.40
Purchase #4	$200.53	7.443%	$215.4554	$215.46	$215.45	$215.50
Purchase #5	$18.33	9.641%	$20.0972	$20.10	$20.10	$20.10
Purchase #6	$85.63	13.316%	$97.0325	$97.03	$97.05	$97.00
Purchase #7	$98.29	8.798%	$106.9376	$106.94	$106.95	$106.90
7 purchase totals =	$851.37		$927.8913	$927.90	$927.90	$927.90