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	$89.54	7.856%	$96.5743	$96.57	$96.55	$96.60
Purchase #2	$160.44	12.547%	$180.5704	$180.57	$180.55	$180.60
Purchase #3	$216.29	11.816%	$241.8468	$241.85	$241.85	$241.80
Purchase #4	$223.31	6.641%	$238.14	$238.14	$238.15	$238.10
Purchase #5	$189.51	3.709%	$196.5389	$196.54	$196.55	$196.50
Purchase #6	$10.57	6.772%	$11.2858	$11.29	$11.30	$11.30
Purchase #7	$146.32	13.852%	$166.5882	$166.59	$166.60	$166.60
7 purchase totals =	$1,035.98		$1,131.5444	$1,131.55	$1,131.55	$1,131.50