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	$171.85	6.474%	$182.9756	$182.98	$183.00	$183.00
Purchase #2	$242.64	3.302%	$250.652	$250.65	$250.65	$250.70
Purchase #3	$13.31	11.473%	$14.8371	$14.84	$14.85	$14.80
Purchase #4	$66.75	3.532%	$69.1076	$69.11	$69.10	$69.10
Purchase #5	$155.59	10.825%	$172.4326	$172.43	$172.45	$172.40
Purchase #6	$142.25	6.838%	$151.9771	$151.98	$152.00	$152.00
Purchase #7	$242.36	11.339%	$269.8412	$269.84	$269.85	$269.80
7 purchase totals =	$1,034.75		$1,111.8232	$1,111.83	$1,111.90	$1,111.80