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	$118.53	12.300%	$133.1092	$133.11	$133.10	$133.10
Purchase #2	$89.41	6.693%	$95.3942	$95.39	$95.40	$95.40
Purchase #3	$103.25	6.456%	$109.9158	$109.92	$109.90	$109.90
Purchase #4	$31.81	10.135%	$35.0339	$35.03	$35.05	$35.00
Purchase #5	$156.48	9.571%	$171.4567	$171.46	$171.45	$171.50
Purchase #6	$244.60	10.854%	$271.1489	$271.15	$271.15	$271.10
Purchase #7	$231.54	7.132%	$248.0534	$248.05	$248.05	$248.10
7 purchase totals =	$975.62		$1,064.1121	$1,064.11	$1,064.10	$1,064.10