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	$238.57	12.191%	$267.6541	$267.65	$267.65	$267.70
Purchase #2	$164.56	12.463%	$185.0691	$185.07	$185.05	$185.10
Purchase #3	$104.46	4.725%	$109.3957	$109.40	$109.40	$109.40
Purchase #4	$17.90	13.158%	$20.2553	$20.26	$20.25	$20.30
Purchase #5	$80.63	5.569%	$85.1203	$85.12	$85.10	$85.10
Purchase #6	$164.61	10.764%	$182.3286	$182.33	$182.35	$182.30
Purchase #7	$181.27	10.662%	$200.597	$200.60	$200.60	$200.60
7 purchase totals =	$952.00		$1,050.4201	$1,050.43	$1,050.40	$1,050.50