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	$242.97	3.119%	$250.5482	$250.55	$250.55	$250.50
Purchase #2	$247.87	6.596%	$264.2195	$264.22	$264.20	$264.20
Purchase #3	$92.80	5.857%	$98.2353	$98.24	$98.25	$98.20
Purchase #4	$17.61	10.109%	$19.3902	$19.39	$19.40	$19.40
Purchase #5	$35.60	10.244%	$39.2469	$39.25	$39.25	$39.20
Purchase #6	$190.28	13.291%	$215.5701	$215.57	$215.55	$215.60
Purchase #7	$136.31	6.127%	$144.6617	$144.66	$144.65	$144.70
7 purchase totals =	$963.44		$1,031.8719	$1,031.88	$1,031.85	$1,031.80