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	$18.37	7.440%	$19.7367	$19.74	$19.75	$19.70
Purchase #2	$219.88	10.466%	$242.8926	$242.89	$242.90	$242.90
Purchase #3	$84.65	5.773%	$89.5368	$89.54	$89.55	$89.50
Purchase #4	$243.78	12.755%	$274.8741	$274.87	$274.85	$274.90
Purchase #5	$50.99	6.865%	$54.4905	$54.49	$54.50	$54.50
Purchase #6	$222.58	5.755%	$235.3895	$235.39	$235.40	$235.40
Purchase #7	$135.68	6.366%	$144.3174	$144.32	$144.30	$144.30
7 purchase totals =	$975.93		$1,061.2376	$1,061.24	$1,061.25	$1,061.20