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	$204.27	8.852%	$222.352	$222.35	$222.35	$222.40
Purchase #2	$161.72	7.829%	$174.3811	$174.38	$174.40	$174.40
Purchase #3	$235.71	6.330%	$250.6304	$250.63	$250.65	$250.60
Purchase #4	$12.71	5.272%	$13.3801	$13.38	$13.40	$13.40
Purchase #5	$174.27	7.497%	$187.335	$187.34	$187.35	$187.30
Purchase #6	$248.47	3.741%	$257.7653	$257.77	$257.75	$257.80
Purchase #7	$5.49	7.280%	$5.8897	$5.89	$5.90	$5.90
7 purchase totals =	$1,042.64		$1,111.7336	$1,111.74	$1,111.80	$1,111.80