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	$219.27	10.423%	$242.1245	$242.12	$242.10	$242.10
Purchase #2	$224.29	3.354%	$231.8127	$231.81	$231.80	$231.80
Purchase #3	$79.80	5.568%	$84.2433	$84.24	$84.25	$84.20
Purchase #4	$233.86	9.194%	$255.3611	$255.36	$255.35	$255.40
Purchase #5	$41.94	3.220%	$43.2905	$43.29	$43.30	$43.30
Purchase #6	$48.83	11.154%	$54.2765	$54.28	$54.30	$54.30
Purchase #7	$235.71	9.629%	$258.4065	$258.41	$258.40	$258.40
7 purchase totals =	$1,083.70		$1,169.5151	$1,169.51	$1,169.50	$1,169.50