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	$183.42	4.587%	$191.8335	$191.83	$191.85	$191.80
Purchase #2	$6.81	8.840%	$7.412	$7.41	$7.40	$7.40
Purchase #3	$215.39	3.710%	$223.381	$223.38	$223.40	$223.40
Purchase #4	$127.28	12.609%	$143.3287	$143.33	$143.35	$143.30
Purchase #5	$138.31	3.573%	$143.2518	$143.25	$143.25	$143.30
Purchase #6	$17.63	4.440%	$18.4128	$18.41	$18.40	$18.40
Purchase #7	$74.38	12.550%	$83.7147	$83.71	$83.70	$83.70
7 purchase totals =	$763.22		$811.3345	$811.32	$811.35	$811.30