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	$193.83	3.409%	$200.4377	$200.44	$200.45	$200.40
Purchase #2	$143.87	3.788%	$149.3198	$149.32	$149.30	$149.30
Purchase #3	$17.73	4.103%	$18.4575	$18.46	$18.45	$18.50
Purchase #4	$36.80	10.580%	$40.6934	$40.69	$40.70	$40.70
Purchase #5	$35.76	6.394%	$38.0465	$38.05	$38.05	$38.00
Purchase #6	$91.85	5.513%	$96.9137	$96.91	$96.90	$96.90
Purchase #7	$200.75	7.570%	$215.9468	$215.95	$215.95	$215.90
7 purchase totals =	$720.59		$759.8154	$759.82	$759.80	$759.70