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	$100.39	9.339%	$109.7654	$109.77	$109.75	$109.80
Purchase #2	$184.52	5.616%	$194.8826	$194.88	$194.90	$194.90
Purchase #3	$192.36	9.257%	$210.1668	$210.17	$210.15	$210.20
Purchase #4	$95.91	8.570%	$104.1295	$104.13	$104.15	$104.10
Purchase #5	$160.70	4.398%	$167.7676	$167.77	$167.75	$167.80
Purchase #6	$34.25	7.219%	$36.7225	$36.72	$36.70	$36.70
Purchase #7	$165.78	8.237%	$179.4353	$179.44	$179.45	$179.40
7 purchase totals =	$933.91		$1,002.8697	$1,002.88	$1,002.85	$1,002.90