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	$87.54	7.794%	$94.3629	$94.36	$94.35	$94.40
Purchase #2	$130.95	11.510%	$146.0223	$146.02	$146.00	$146.00
Purchase #3	$230.91	12.146%	$258.9563	$258.96	$258.95	$259.00
Purchase #4	$38.33	10.383%	$42.3098	$42.31	$42.30	$42.30
Purchase #5	$117.46	5.400%	$123.8028	$123.80	$123.80	$123.80
Purchase #6	$126.67	12.649%	$142.6925	$142.69	$142.70	$142.70
Purchase #7	$188.96	4.506%	$197.4745	$197.47	$197.45	$197.50
7 purchase totals =	$920.82		$1,005.6211	$1,005.61	$1,005.55	$1,005.70