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	$158.35	5.659%	$167.311	$167.31	$167.30	$167.30
Purchase #2	$160.83	4.252%	$167.6685	$167.67	$167.65	$167.70
Purchase #3	$84.41	6.497%	$89.8941	$89.89	$89.90	$89.90
Purchase #4	$135.99	4.534%	$142.1558	$142.16	$142.15	$142.20
Purchase #5	$112.67	9.712%	$123.6125	$123.61	$123.60	$123.60
Purchase #6	$247.47	8.271%	$267.9382	$267.94	$267.95	$267.90
Purchase #7	$173.54	10.361%	$191.5205	$191.52	$191.50	$191.50
7 purchase totals =	$1,073.26		$1,150.1006	$1,150.10	$1,150.05	$1,150.10