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	$223.51	7.814%	$240.9751	$240.98	$241.00	$241.00
Purchase #2	$116.64	10.515%	$128.9047	$128.90	$128.90	$128.90
Purchase #3	$144.25	4.599%	$150.8841	$150.88	$150.90	$150.90
Purchase #4	$60.64	11.662%	$67.7118	$67.71	$67.70	$67.70
Purchase #5	$47.99	8.630%	$52.1315	$52.13	$52.15	$52.10
Purchase #6	$51.50	4.689%	$53.9148	$53.91	$53.90	$53.90
Purchase #7	$52.45	10.581%	$57.9997	$58.00	$58.00	$58.00
7 purchase totals =	$696.98		$752.5217	$752.51	$752.55	$752.50