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	$173.83	6.703%	$185.4818	$185.48	$185.50	$185.50
Purchase #2	$212.97	13.545%	$241.8168	$241.82	$241.80	$241.80
Purchase #3	$86.53	5.533%	$91.3177	$91.32	$91.30	$91.30
Purchase #4	$126.98	10.695%	$140.5605	$140.56	$140.55	$140.60
Purchase #5	$144.76	11.476%	$161.3727	$161.37	$161.35	$161.40
Purchase #6	$143.35	6.574%	$152.7738	$152.77	$152.75	$152.80
Purchase #7	$100.31	9.608%	$109.9478	$109.95	$109.95	$109.90
7 purchase totals =	$988.73		$1,083.2711	$1,083.27	$1,083.20	$1,083.30