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	$98.50	13.552%	$111.8487	$111.85	$111.85	$111.80
Purchase #2	$76.72	11.823%	$85.7906	$85.79	$85.80	$85.80
Purchase #3	$96.37	7.812%	$103.8984	$103.90	$103.90	$103.90
Purchase #4	$129.36	3.451%	$133.8242	$133.82	$133.80	$133.80
Purchase #5	$112.49	13.653%	$127.8483	$127.85	$127.85	$127.80
Purchase #6	$42.58	10.710%	$47.1403	$47.14	$47.15	$47.10
Purchase #7	$172.57	4.813%	$180.8758	$180.88	$180.90	$180.90
7 purchase totals =	$728.59		$791.2263	$791.23	$791.25	$791.10