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	$167.71	8.845%	$182.5439	$182.54	$182.55	$182.50
Purchase #2	$29.57	9.471%	$32.3706	$32.37	$32.35	$32.40
Purchase #3	$174.60	4.441%	$182.354	$182.35	$182.35	$182.40
Purchase #4	$173.56	12.872%	$195.9006	$195.90	$195.90	$195.90
Purchase #5	$64.96	6.621%	$69.261	$69.26	$69.25	$69.30
Purchase #6	$209.91	13.809%	$238.8965	$238.90	$238.90	$238.90
Purchase #7	$185.38	3.404%	$191.6903	$191.69	$191.70	$191.70
7 purchase totals =	$1,005.69		$1,093.0169	$1,093.01	$1,093.00	$1,093.10