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	$197.51	12.798%	$222.7873	$222.79	$222.80	$222.80
Purchase #2	$225.89	10.723%	$250.1122	$250.11	$250.10	$250.10
Purchase #3	$75.52	9.383%	$82.606	$82.61	$82.60	$82.60
Purchase #4	$226.33	9.456%	$247.7318	$247.73	$247.75	$247.70
Purchase #5	$38.28	13.186%	$43.3276	$43.33	$43.35	$43.30
Purchase #6	$112.81	9.514%	$123.5427	$123.54	$123.55	$123.50
Purchase #7	$74.34	10.819%	$82.3828	$82.38	$82.40	$82.40
7 purchase totals =	$950.68		$1,052.4904	$1,052.49	$1,052.55	$1,052.40