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	$205.97	9.681%	$225.91	$225.91	$225.90	$225.90
Purchase #2	$245.40	7.407%	$263.5768	$263.58	$263.60	$263.60
Purchase #3	$33.58	11.122%	$37.3148	$37.31	$37.30	$37.30
Purchase #4	$176.31	7.484%	$189.505	$189.51	$189.50	$189.50
Purchase #5	$175.55	9.718%	$192.6099	$192.61	$192.60	$192.60
Purchase #6	$80.60	9.515%	$88.2691	$88.27	$88.25	$88.30
Purchase #7	$182.70	4.462%	$190.8521	$190.85	$190.85	$190.90
7 purchase totals =	$1,100.11		$1,188.0377	$1,188.04	$1,188.00	$1,188.10