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	$189.74	3.561%	$196.4966	$196.50	$196.50	$196.50
Purchase #2	$188.99	11.804%	$211.2984	$211.30	$211.30	$211.30
Purchase #3	$55.79	5.106%	$58.6386	$58.64	$58.65	$58.60
Purchase #4	$143.76	3.266%	$148.4552	$148.46	$148.45	$148.50
Purchase #5	$87.81	3.475%	$90.8614	$90.86	$90.85	$90.90
Purchase #6	$94.26	9.247%	$102.9762	$102.98	$103.00	$103.00
Purchase #7	$41.92	4.295%	$43.7205	$43.72	$43.70	$43.70
7 purchase totals =	$802.27		$852.4469	$852.46	$852.45	$852.50