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	$151.83	13.221%	$171.9034	$171.90	$171.90	$171.90
Purchase #2	$75.59	4.250%	$78.8026	$78.80	$78.80	$78.80
Purchase #3	$90.33	4.457%	$94.356	$94.36	$94.35	$94.40
Purchase #4	$135.69	8.530%	$147.2644	$147.26	$147.25	$147.30
Purchase #5	$105.43	12.731%	$118.8523	$118.85	$118.85	$118.90
Purchase #6	$32.41	11.524%	$36.1449	$36.14	$36.15	$36.10
Purchase #7	$36.79	13.565%	$41.7806	$41.78	$41.80	$41.80
7 purchase totals =	$628.07		$689.1042	$689.09	$689.10	$689.20