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	$179.67	11.675%	$200.6465	$200.65	$200.65	$200.60
Purchase #2	$233.52	8.457%	$253.2688	$253.27	$253.25	$253.30
Purchase #3	$140.84	7.445%	$151.3255	$151.33	$151.35	$151.30
Purchase #4	$30.51	6.162%	$32.39	$32.39	$32.40	$32.40
Purchase #5	$215.30	11.654%	$240.3911	$240.39	$240.40	$240.40
Purchase #6	$85.60	6.536%	$91.1948	$91.19	$91.20	$91.20
Purchase #7	$71.83	11.383%	$80.0064	$80.01	$80.00	$80.00
7 purchase totals =	$957.27		$1,049.2231	$1,049.23	$1,049.25	$1,049.20