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	$49.59	5.424%	$52.2798	$52.28	$52.30	$52.30
Purchase #2	$204.61	9.182%	$223.3973	$223.40	$223.40	$223.40
Purchase #3	$205.39	3.659%	$212.9052	$212.91	$212.90	$212.90
Purchase #4	$210.83	3.665%	$218.5569	$218.56	$218.55	$218.60
Purchase #5	$114.64	9.741%	$125.8071	$125.81	$125.80	$125.80
Purchase #6	$52.70	7.170%	$56.4786	$56.48	$56.50	$56.50
Purchase #7	$103.77	10.151%	$114.3037	$114.30	$114.30	$114.30
7 purchase totals =	$941.53		$1,003.7286	$1,003.74	$1,003.75	$1,003.80