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	$250.27	13.155%	$283.193	$283.19	$283.20	$283.20
Purchase #2	$58.71	5.309%	$61.8269	$61.83	$61.85	$61.80
Purchase #3	$100.79	9.516%	$110.3812	$110.38	$110.40	$110.40
Purchase #4	$41.36	3.321%	$42.7336	$42.73	$42.75	$42.70
Purchase #5	$190.52	5.235%	$200.4937	$200.49	$200.50	$200.50
Purchase #6	$234.77	9.816%	$257.815	$257.82	$257.80	$257.80
Purchase #7	$73.78	11.296%	$82.1142	$82.11	$82.10	$82.10
7 purchase totals =	$950.20		$1,038.5576	$1,038.55	$1,038.60	$1,038.50