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	$95.54	12.156%	$107.1538	$107.15	$107.15	$107.20
Purchase #2	$111.73	10.416%	$123.3678	$123.37	$123.35	$123.40
Purchase #3	$25.45	4.682%	$26.6416	$26.64	$26.65	$26.60
Purchase #4	$227.79	7.681%	$245.2865	$245.29	$245.30	$245.30
Purchase #5	$85.35	11.182%	$94.8938	$94.89	$94.90	$94.90
Purchase #6	$233.37	9.215%	$254.875	$254.88	$254.90	$254.90
Purchase #7	$193.83	7.621%	$208.6018	$208.60	$208.60	$208.60
7 purchase totals =	$973.06		$1,060.8203	$1,060.82	$1,060.85	$1,060.90