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	$232.69	6.834%	$248.592	$248.59	$248.60	$248.60
Purchase #2	$95.93	4.314%	$100.0684	$100.07	$100.05	$100.10
Purchase #3	$236.50	7.235%	$253.6108	$253.61	$253.60	$253.60
Purchase #4	$18.77	10.364%	$20.7153	$20.72	$20.70	$20.70
Purchase #5	$250.50	4.559%	$261.9203	$261.92	$261.90	$261.90
Purchase #6	$51.54	4.839%	$54.034	$54.03	$54.05	$54.00
Purchase #7	$82.38	10.323%	$90.8841	$90.88	$90.90	$90.90
7 purchase totals =	$968.31		$1,029.8249	$1,029.82	$1,029.80	$1,029.80