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	$177.97	5.267%	$187.3437	$187.34	$187.35	$187.30
Purchase #2	$176.65	11.673%	$197.2704	$197.27	$197.25	$197.30
Purchase #3	$95.54	4.232%	$99.5833	$99.58	$99.60	$99.60
Purchase #4	$52.29	13.380%	$59.2864	$59.29	$59.30	$59.30
Purchase #5	$223.94	9.797%	$245.8794	$245.88	$245.90	$245.90
Purchase #6	$96.28	7.359%	$103.3652	$103.37	$103.35	$103.40
Purchase #7	$205.90	6.794%	$219.8888	$219.89	$219.90	$219.90
7 purchase totals =	$1,028.57		$1,112.6172	$1,112.62	$1,112.65	$1,112.70