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	$94.87	5.558%	$100.1429	$100.14	$100.15	$100.10
Purchase #2	$226.65	7.386%	$243.3904	$243.39	$243.40	$243.40
Purchase #3	$247.64	6.141%	$262.8476	$262.85	$262.85	$262.80
Purchase #4	$30.92	9.533%	$33.8676	$33.87	$33.85	$33.90
Purchase #5	$89.69	9.777%	$98.459	$98.46	$98.45	$98.50
Purchase #6	$58.35	7.421%	$62.6802	$62.68	$62.70	$62.70
Purchase #7	$103.42	9.386%	$113.127	$113.13	$113.15	$113.10
7 purchase totals =	$851.54		$914.5147	$914.52	$914.55	$914.50