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	$142.67	5.417%	$150.3984	$150.40	$150.40	$150.40
Purchase #2	$33.59	13.668%	$38.1811	$38.18	$38.20	$38.20
Purchase #3	$27.84	3.252%	$28.7454	$28.75	$28.75	$28.70
Purchase #4	$53.93	10.284%	$59.4762	$59.48	$59.50	$59.50
Purchase #5	$47.67	10.538%	$52.6935	$52.69	$52.70	$52.70
Purchase #6	$172.70	5.244%	$181.7564	$181.76	$181.75	$181.80
Purchase #7	$51.87	3.266%	$53.5641	$53.56	$53.55	$53.60
7 purchase totals =	$530.27		$564.8151	$564.82	$564.85	$564.90