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	$160.59	13.439%	$182.1717	$182.17	$182.15	$182.20
Purchase #2	$213.73	11.115%	$237.4861	$237.49	$237.50	$237.50
Purchase #3	$162.78	5.381%	$171.5392	$171.54	$171.55	$171.50
Purchase #4	$72.80	8.305%	$78.846	$78.85	$78.85	$78.80
Purchase #5	$91.29	6.834%	$97.5288	$97.53	$97.55	$97.50
Purchase #6	$50.28	7.126%	$53.863	$53.86	$53.85	$53.90
Purchase #7	$156.44	6.253%	$166.2222	$166.22	$166.20	$166.20
7 purchase totals =	$907.91		$987.6570	$987.66	$987.65	$987.60