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	$118.40	7.684%	$127.4979	$127.50	$127.50	$127.50
Purchase #2	$43.48	13.432%	$49.3202	$49.32	$49.30	$49.30
Purchase #3	$204.90	7.629%	$220.5318	$220.53	$220.55	$220.50
Purchase #4	$45.27	12.132%	$50.7622	$50.76	$50.75	$50.80
Purchase #5	$64.71	4.831%	$67.8361	$67.84	$67.85	$67.80
Purchase #6	$115.87	6.857%	$123.8152	$123.82	$123.80	$123.80
Purchase #7	$163.48	11.543%	$182.3505	$182.35	$182.35	$182.40
7 purchase totals =	$756.11		$822.1139	$822.12	$822.10	$822.10