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	$104.43	3.298%	$107.8741	$107.87	$107.85	$107.90
Purchase #2	$211.27	10.738%	$233.9562	$233.96	$233.95	$234.00
Purchase #3	$179.80	9.165%	$196.2787	$196.28	$196.30	$196.30
Purchase #4	$155.27	7.499%	$166.9137	$166.91	$166.90	$166.90
Purchase #5	$87.72	13.405%	$99.4789	$99.48	$99.50	$99.50
Purchase #6	$134.55	4.841%	$141.0636	$141.06	$141.05	$141.10
Purchase #7	$197.46	5.379%	$208.0814	$208.08	$208.10	$208.10
7 purchase totals =	$1,070.50		$1,153.6466	$1,153.64	$1,153.65	$1,153.80