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	$51.59	4.497%	$53.91	$53.91	$53.90	$53.90
Purchase #2	$205.51	9.416%	$224.8608	$224.86	$224.85	$224.90
Purchase #3	$88.80	4.181%	$92.5127	$92.51	$92.50	$92.50
Purchase #4	$73.34	12.718%	$82.6674	$82.67	$82.65	$82.70
Purchase #5	$203.82	5.598%	$215.2298	$215.23	$215.25	$215.20
Purchase #6	$158.63	5.674%	$167.6307	$167.63	$167.65	$167.60
Purchase #7	$161.62	12.784%	$182.2815	$182.28	$182.30	$182.30
7 purchase totals =	$943.31		$1,019.0929	$1,019.09	$1,019.10	$1,019.10