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	$190.40	11.103%	$211.5401	$211.54	$211.55	$211.50
Purchase #2	$58.65	11.703%	$65.5138	$65.51	$65.50	$65.50
Purchase #3	$120.74	12.815%	$136.2128	$136.21	$136.20	$136.20
Purchase #4	$148.79	13.219%	$168.4586	$168.46	$168.45	$168.50
Purchase #5	$138.39	4.424%	$144.5124	$144.51	$144.50	$144.50
Purchase #6	$111.30	4.209%	$115.9846	$115.98	$116.00	$116.00
Purchase #7	$62.28	5.515%	$65.7147	$65.71	$65.70	$65.70
7 purchase totals =	$830.55		$907.9370	$907.92	$907.90	$907.90