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	$79.88	6.793%	$85.3062	$85.31	$85.30	$85.30
Purchase #2	$117.46	6.411%	$124.9904	$124.99	$125.00	$125.00
Purchase #3	$177.80	7.268%	$190.7225	$190.72	$190.70	$190.70
Purchase #4	$241.95	12.673%	$272.6123	$272.61	$272.60	$272.60
Purchase #5	$125.88	8.227%	$136.2361	$136.24	$136.25	$136.20
Purchase #6	$190.61	10.469%	$210.565	$210.57	$210.55	$210.60
Purchase #7	$127.54	11.728%	$142.4979	$142.50	$142.50	$142.50
7 purchase totals =	$1,061.12		$1,162.9304	$1,162.94	$1,162.90	$1,162.90