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	$87.90	4.137%	$91.5364	$91.54	$91.55	$91.50
Purchase #2	$229.44	6.721%	$244.8607	$244.86	$244.85	$244.90
Purchase #3	$186.61	4.128%	$194.3133	$194.31	$194.30	$194.30
Purchase #4	$208.47	5.631%	$220.2089	$220.21	$220.20	$220.20
Purchase #5	$33.48	12.865%	$37.7872	$37.79	$37.80	$37.80
Purchase #6	$80.85	10.116%	$89.0288	$89.03	$89.05	$89.00
Purchase #7	$182.76	4.826%	$191.58	$191.58	$191.60	$191.60
7 purchase totals =	$1,009.51		$1,069.3153	$1,069.32	$1,069.35	$1,069.30