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	$185.65	11.443%	$206.8939	$206.89	$206.90	$206.90
Purchase #2	$191.69	11.323%	$213.3951	$213.40	$213.40	$213.40
Purchase #3	$18.96	8.347%	$20.5426	$20.54	$20.55	$20.50
Purchase #4	$178.82	6.483%	$190.4129	$190.41	$190.40	$190.40
Purchase #5	$20.46	8.269%	$22.1518	$22.15	$22.15	$22.20
Purchase #6	$217.35	12.171%	$243.8037	$243.80	$243.80	$243.80
Purchase #7	$102.65	11.554%	$114.5102	$114.51	$114.50	$114.50
7 purchase totals =	$915.58		$1,011.7102	$1,011.70	$1,011.70	$1,011.70