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	$182.65	5.829%	$193.2967	$193.30	$193.30	$193.30
Purchase #2	$171.73	8.262%	$185.9183	$185.92	$185.90	$185.90
Purchase #3	$79.54	4.261%	$82.9292	$82.93	$82.95	$82.90
Purchase #4	$119.68	3.803%	$124.2314	$124.23	$124.25	$124.20
Purchase #5	$173.78	10.134%	$191.3909	$191.39	$191.40	$191.40
Purchase #6	$212.90	9.703%	$233.5577	$233.56	$233.55	$233.60
Purchase #7	$41.28	12.621%	$46.4899	$46.49	$46.50	$46.50
7 purchase totals =	$981.56		$1,057.8141	$1,057.82	$1,057.85	$1,057.80