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	$127.53	13.271%	$144.4545	$144.45	$144.45	$144.50
Purchase #2	$222.67	3.799%	$231.1292	$231.13	$231.15	$231.10
Purchase #3	$228.86	3.435%	$236.7213	$236.72	$236.70	$236.70
Purchase #4	$96.95	12.557%	$109.124	$109.12	$109.10	$109.10
Purchase #5	$219.52	6.803%	$234.4539	$234.45	$234.45	$234.50
Purchase #6	$59.60	4.254%	$62.1354	$62.14	$62.15	$62.10
Purchase #7	$116.83	10.256%	$128.8121	$128.81	$128.80	$128.80
7 purchase totals =	$1,071.96		$1,146.8304	$1,146.82	$1,146.80	$1,146.80