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	$53.58	10.122%	$59.0034	$59.00	$59.00	$59.00
Purchase #2	$162.36	7.304%	$174.2188	$174.22	$174.20	$174.20
Purchase #3	$158.25	6.652%	$168.7768	$168.78	$168.80	$168.80
Purchase #4	$162.48	13.788%	$184.8827	$184.88	$184.90	$184.90
Purchase #5	$196.98	8.255%	$213.2407	$213.24	$213.25	$213.20
Purchase #6	$185.81	4.139%	$193.5007	$193.50	$193.50	$193.50
Purchase #7	$165.56	3.116%	$170.7188	$170.72	$170.70	$170.70
7 purchase totals =	$1,085.02		$1,164.3419	$1,164.34	$1,164.35	$1,164.30