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	$86.93	5.483%	$91.6964	$91.70	$91.70	$91.70
Purchase #2	$148.56	13.476%	$168.5799	$168.58	$168.60	$168.60
Purchase #3	$15.85	9.277%	$17.3204	$17.32	$17.30	$17.30
Purchase #4	$52.76	12.245%	$59.2205	$59.22	$59.20	$59.20
Purchase #5	$243.93	3.269%	$251.9041	$251.90	$251.90	$251.90
Purchase #6	$144.56	10.865%	$160.2664	$160.27	$160.25	$160.30
Purchase #7	$213.38	7.419%	$229.2107	$229.21	$229.20	$229.20
7 purchase totals =	$905.97		$978.1984	$978.20	$978.15	$978.20