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	$202.70	5.711%	$214.2762	$214.28	$214.30	$214.30
Purchase #2	$33.87	13.398%	$38.4079	$38.41	$38.40	$38.40
Purchase #3	$103.57	12.587%	$116.6064	$116.61	$116.60	$116.60
Purchase #4	$66.27	11.308%	$73.7638	$73.76	$73.75	$73.80
Purchase #5	$64.65	12.445%	$72.6957	$72.70	$72.70	$72.70
Purchase #6	$187.46	6.762%	$200.136	$200.14	$200.15	$200.10
Purchase #7	$221.32	5.650%	$233.8246	$233.82	$233.80	$233.80
7 purchase totals =	$879.84		$949.7106	$949.72	$949.70	$949.70