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	$164.30	5.817%	$173.8573	$173.86	$173.85	$173.90
Purchase #2	$160.46	7.458%	$172.4271	$172.43	$172.45	$172.40
Purchase #3	$90.56	11.580%	$101.0468	$101.05	$101.05	$101.00
Purchase #4	$181.59	13.607%	$206.299	$206.30	$206.30	$206.30
Purchase #5	$76.27	7.608%	$82.0726	$82.07	$82.05	$82.10
Purchase #6	$125.60	12.662%	$141.5035	$141.50	$141.50	$141.50
Purchase #7	$79.64	8.291%	$86.243	$86.24	$86.25	$86.20
7 purchase totals =	$878.42		$963.4493	$963.45	$963.45	$963.40