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	$71.33	11.591%	$79.5979	$79.60	$79.60	$79.60
Purchase #2	$21.71	4.387%	$22.6624	$22.66	$22.65	$22.70
Purchase #3	$250.88	7.335%	$269.282	$269.28	$269.30	$269.30
Purchase #4	$100.33	12.108%	$112.478	$112.48	$112.50	$112.50
Purchase #5	$182.92	6.521%	$194.8482	$194.85	$194.85	$194.80
Purchase #6	$116.52	11.803%	$130.2729	$130.27	$130.25	$130.30
Purchase #7	$119.80	6.801%	$127.9476	$127.95	$127.95	$127.90
7 purchase totals =	$863.49		$937.0890	$937.09	$937.10	$937.10