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	$82.46	11.343%	$91.8134	$91.81	$91.80	$91.80
Purchase #2	$186.85	12.126%	$209.5074	$209.51	$209.50	$209.50
Purchase #3	$223.93	11.413%	$249.4871	$249.49	$249.50	$249.50
Purchase #4	$187.40	12.398%	$210.6339	$210.63	$210.65	$210.60
Purchase #5	$92.55	4.180%	$96.4186	$96.42	$96.40	$96.40
Purchase #6	$142.66	11.201%	$158.6393	$158.64	$158.65	$158.60
Purchase #7	$166.40	10.288%	$183.5192	$183.52	$183.50	$183.50
7 purchase totals =	$1,082.25		$1,200.0189	$1,200.02	$1,200.00	$1,199.90