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	$125.26	13.716%	$142.4407	$142.44	$142.45	$142.40
Purchase #2	$125.47	3.176%	$129.4549	$129.45	$129.45	$129.50
Purchase #3	$225.59	3.488%	$233.4586	$233.46	$233.45	$233.50
Purchase #4	$135.91	4.797%	$142.4296	$142.43	$142.45	$142.40
Purchase #5	$162.70	3.554%	$168.4824	$168.48	$168.50	$168.50
Purchase #6	$33.39	11.754%	$37.3147	$37.31	$37.30	$37.30
Purchase #7	$122.37	9.162%	$133.5815	$133.58	$133.60	$133.60
7 purchase totals =	$930.69		$987.1624	$987.15	$987.20	$987.20