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	$244.84	6.768%	$261.4108	$261.41	$261.40	$261.40
Purchase #2	$6.81	8.521%	$7.3903	$7.39	$7.40	$7.40
Purchase #3	$203.54	12.802%	$229.5972	$229.60	$229.60	$229.60
Purchase #4	$184.91	7.618%	$198.9964	$199.00	$199.00	$199.00
Purchase #5	$23.77	5.713%	$25.128	$25.13	$25.15	$25.10
Purchase #6	$160.51	6.593%	$171.0924	$171.09	$171.10	$171.10
Purchase #7	$161.77	6.865%	$172.8755	$172.88	$172.90	$172.90
7 purchase totals =	$986.15		$1,066.4906	$1,066.50	$1,066.55	$1,066.50