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	$234.81	5.568%	$247.8842	$247.88	$247.90	$247.90
Purchase #2	$162.27	7.605%	$174.6106	$174.61	$174.60	$174.60
Purchase #3	$176.26	10.348%	$194.4994	$194.50	$194.50	$194.50
Purchase #4	$179.64	3.316%	$185.5969	$185.60	$185.60	$185.60
Purchase #5	$92.47	4.232%	$96.3833	$96.38	$96.40	$96.40
Purchase #6	$230.61	11.221%	$256.4867	$256.49	$256.50	$256.50
Purchase #7	$95.53	3.296%	$98.6787	$98.68	$98.70	$98.70
7 purchase totals =	$1,171.59		$1,254.1398	$1,254.14	$1,254.20	$1,254.20