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	$213.26	4.278%	$222.3833	$222.38	$222.40	$222.40
Purchase #2	$119.65	11.663%	$133.6048	$133.60	$133.60	$133.60
Purchase #3	$212.85	6.342%	$226.3489	$226.35	$226.35	$226.30
Purchase #4	$156.55	3.705%	$162.3502	$162.35	$162.35	$162.40
Purchase #5	$223.95	3.327%	$231.4008	$231.40	$231.40	$231.40
Purchase #6	$248.60	13.362%	$281.8179	$281.82	$281.80	$281.80
Purchase #7	$94.92	6.258%	$100.8601	$100.86	$100.85	$100.90
7 purchase totals =	$1,269.78		$1,358.7660	$1,358.76	$1,358.75	$1,358.80