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	$105.73	3.227%	$109.1419	$109.14	$109.15	$109.10
Purchase #2	$98.84	4.153%	$102.9448	$102.94	$102.95	$102.90
Purchase #3	$164.55	3.271%	$169.9324	$169.93	$169.95	$169.90
Purchase #4	$215.98	3.107%	$222.6905	$222.69	$222.70	$222.70
Purchase #5	$113.72	12.355%	$127.7701	$127.77	$127.75	$127.80
Purchase #6	$159.40	9.442%	$174.4505	$174.45	$174.45	$174.50
Purchase #7	$113.68	12.219%	$127.5706	$127.57	$127.55	$127.60
7 purchase totals =	$971.90		$1,034.5008	$1,034.49	$1,034.50	$1,034.50