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	$168.73	5.679%	$178.3122	$178.31	$178.30	$178.30
Purchase #2	$135.80	13.433%	$154.042	$154.04	$154.05	$154.00
Purchase #3	$200.37	6.555%	$213.5043	$213.50	$213.50	$213.50
Purchase #4	$91.55	9.299%	$100.0632	$100.06	$100.05	$100.10
Purchase #5	$156.50	9.618%	$171.5522	$171.55	$171.55	$171.60
Purchase #6	$88.68	4.418%	$92.5979	$92.60	$92.60	$92.60
Purchase #7	$209.50	11.526%	$233.647	$233.65	$233.65	$233.60
7 purchase totals =	$1,051.13		$1,143.7188	$1,143.71	$1,143.70	$1,143.70