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	$238.87	4.850%	$250.4552	$250.46	$250.45	$250.50
Purchase #2	$6.30	9.813%	$6.9182	$6.92	$6.90	$6.90
Purchase #3	$38.50	11.474%	$42.9175	$42.92	$42.90	$42.90
Purchase #4	$9.56	13.467%	$10.8474	$10.85	$10.85	$10.80
Purchase #5	$193.42	10.265%	$213.2746	$213.27	$213.25	$213.30
Purchase #6	$157.66	8.711%	$171.3938	$171.39	$171.40	$171.40
Purchase #7	$163.93	9.734%	$179.8869	$179.89	$179.90	$179.90
7 purchase totals =	$808.24		$875.6936	$875.70	$875.65	$875.70