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	$83.98	8.194%	$90.8613	$90.86	$90.85	$90.90
Purchase #2	$79.45	13.179%	$89.9207	$89.92	$89.90	$89.90
Purchase #3	$193.61	5.748%	$204.7387	$204.74	$204.75	$204.70
Purchase #4	$172.73	3.255%	$178.3524	$178.35	$178.35	$178.40
Purchase #5	$47.42	13.546%	$53.8435	$53.84	$53.85	$53.80
Purchase #6	$180.33	4.348%	$188.1707	$188.17	$188.15	$188.20
Purchase #7	$191.68	4.648%	$200.5893	$200.59	$200.60	$200.60
7 purchase totals =	$949.20		$1,006.4766	$1,006.47	$1,006.45	$1,006.50