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	$44.96	11.510%	$50.1349	$50.13	$50.15	$50.10
Purchase #2	$40.71	7.197%	$43.6399	$43.64	$43.65	$43.60
Purchase #3	$71.45	4.764%	$74.8539	$74.85	$74.85	$74.90
Purchase #4	$98.43	13.729%	$111.9435	$111.94	$111.95	$111.90
Purchase #5	$205.40	11.650%	$229.3291	$229.33	$229.35	$229.30
Purchase #6	$132.57	6.692%	$141.4416	$141.44	$141.45	$141.40
Purchase #7	$53.66	3.602%	$55.5928	$55.59	$55.60	$55.60
7 purchase totals =	$647.18		$706.9357	$706.92	$707.00	$706.80