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	$87.79	10.171%	$96.7191	$96.72	$96.70	$96.70
Purchase #2	$60.97	11.355%	$67.8931	$67.89	$67.90	$67.90
Purchase #3	$158.40	5.485%	$167.0882	$167.09	$167.10	$167.10
Purchase #4	$164.76	4.375%	$171.9683	$171.97	$171.95	$172.00
Purchase #5	$215.81	6.572%	$229.993	$229.99	$230.00	$230.00
Purchase #6	$144.87	4.872%	$151.9281	$151.93	$151.95	$151.90
Purchase #7	$123.59	6.537%	$131.6691	$131.67	$131.65	$131.70
7 purchase totals =	$956.19		$1,017.2589	$1,017.26	$1,017.25	$1,017.30