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	$143.76	5.744%	$152.0176	$152.02	$152.00	$152.00
Purchase #2	$31.71	6.846%	$33.8809	$33.88	$33.90	$33.90
Purchase #3	$113.83	12.392%	$127.9358	$127.94	$127.95	$127.90
Purchase #4	$241.38	10.318%	$266.2856	$266.29	$266.30	$266.30
Purchase #5	$26.47	7.736%	$28.5177	$28.52	$28.50	$28.50
Purchase #6	$65.31	10.103%	$71.9083	$71.91	$71.90	$71.90
Purchase #7	$60.30	8.469%	$65.4068	$65.41	$65.40	$65.40
7 purchase totals =	$682.76		$745.9527	$745.97	$745.95	$745.90