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	$41.27	9.372%	$45.1378	$45.14	$45.15	$45.10
Purchase #2	$184.46	13.122%	$208.6648	$208.66	$208.65	$208.70
Purchase #3	$173.75	13.205%	$196.6937	$196.69	$196.70	$196.70
Purchase #4	$188.51	11.397%	$209.9945	$209.99	$210.00	$210.00
Purchase #5	$31.33	4.357%	$32.695	$32.70	$32.70	$32.70
Purchase #6	$43.81	3.404%	$45.3013	$45.30	$45.30	$45.30
Purchase #7	$120.73	6.565%	$128.6559	$128.66	$128.65	$128.70
7 purchase totals =	$783.86		$867.1430	$867.14	$867.15	$867.20