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	$126.72	5.287%	$133.4197	$133.42	$133.40	$133.40
Purchase #2	$179.45	3.330%	$185.4257	$185.43	$185.45	$185.40
Purchase #3	$158.93	5.829%	$168.194	$168.19	$168.20	$168.20
Purchase #4	$160.92	6.763%	$171.803	$171.80	$171.80	$171.80
Purchase #5	$53.63	11.402%	$59.7449	$59.74	$59.75	$59.70
Purchase #6	$234.84	6.533%	$250.1821	$250.18	$250.20	$250.20
Purchase #7	$169.41	10.610%	$187.3844	$187.38	$187.40	$187.40
7 purchase totals =	$1,083.90		$1,156.1538	$1,156.14	$1,156.20	$1,156.10