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	$224.29	11.832%	$250.828	$250.83	$250.85	$250.80
Purchase #2	$57.59	8.550%	$62.5139	$62.51	$62.50	$62.50
Purchase #3	$144.56	9.141%	$157.7742	$157.77	$157.75	$157.80
Purchase #4	$79.46	7.709%	$85.5856	$85.59	$85.60	$85.60
Purchase #5	$175.97	4.514%	$183.9133	$183.91	$183.90	$183.90
Purchase #6	$209.56	4.738%	$219.489	$219.49	$219.50	$219.50
Purchase #7	$43.88	3.759%	$45.5294	$45.53	$45.55	$45.50
7 purchase totals =	$935.31		$1,005.6334	$1,005.63	$1,005.65	$1,005.60