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	$146.94	12.801%	$165.7498	$165.75	$165.75	$165.70
Purchase #2	$102.63	7.229%	$110.0491	$110.05	$110.05	$110.00
Purchase #3	$59.91	10.334%	$66.1011	$66.10	$66.10	$66.10
Purchase #4	$186.25	12.380%	$209.3078	$209.31	$209.30	$209.30
Purchase #5	$152.93	9.379%	$167.2733	$167.27	$167.25	$167.30
Purchase #6	$52.28	13.807%	$59.4983	$59.50	$59.50	$59.50
Purchase #7	$201.40	8.851%	$219.2259	$219.23	$219.25	$219.20
7 purchase totals =	$902.34		$997.2053	$997.21	$997.20	$997.10