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	$46.89	7.103%	$50.2206	$50.22	$50.20	$50.20
Purchase #2	$22.92	7.256%	$24.5831	$24.58	$24.60	$24.60
Purchase #3	$24.76	13.465%	$28.0939	$28.09	$28.10	$28.10
Purchase #4	$113.93	11.469%	$126.9966	$127.00	$127.00	$127.00
Purchase #5	$22.79	6.745%	$24.3272	$24.33	$24.35	$24.30
Purchase #6	$67.83	5.346%	$71.4562	$71.46	$71.45	$71.50
Purchase #7	$87.53	13.578%	$99.4148	$99.41	$99.40	$99.40
7 purchase totals =	$386.65		$425.0924	$425.09	$425.10	$425.10