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	$191.86	7.583%	$206.4087	$206.41	$206.40	$206.40
Purchase #2	$52.88	12.389%	$59.4313	$59.43	$59.45	$59.40
Purchase #3	$213.70	7.173%	$229.0287	$229.03	$229.05	$229.00
Purchase #4	$25.47	8.169%	$27.5506	$27.55	$27.55	$27.60
Purchase #5	$218.27	9.203%	$238.3574	$238.36	$238.35	$238.40
Purchase #6	$126.46	5.776%	$133.7643	$133.76	$133.75	$133.80
Purchase #7	$226.82	10.625%	$250.9196	$250.92	$250.90	$250.90
7 purchase totals =	$1,055.46		$1,145.4606	$1,145.46	$1,145.45	$1,145.50