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	$17.43	9.699%	$19.1205	$19.12	$19.10	$19.10
Purchase #2	$79.69	5.290%	$83.9056	$83.91	$83.90	$83.90
Purchase #3	$99.42	6.438%	$105.8207	$105.82	$105.80	$105.80
Purchase #4	$248.51	3.386%	$256.9245	$256.92	$256.90	$256.90
Purchase #5	$180.27	13.471%	$204.5542	$204.55	$204.55	$204.60
Purchase #6	$237.31	5.228%	$249.7166	$249.72	$249.70	$249.70
Purchase #7	$182.54	7.626%	$196.4605	$196.46	$196.45	$196.50
7 purchase totals =	$1,045.17		$1,116.5026	$1,116.50	$1,116.40	$1,116.50