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	$93.89	3.717%	$97.3799	$97.38	$97.40	$97.40
Purchase #2	$55.59	3.356%	$57.4556	$57.46	$57.45	$57.50
Purchase #3	$69.75	3.573%	$72.2422	$72.24	$72.25	$72.20
Purchase #4	$140.39	11.218%	$156.139	$156.14	$156.15	$156.10
Purchase #5	$144.95	7.631%	$156.0111	$156.01	$156.00	$156.00
Purchase #6	$51.69	13.448%	$58.6413	$58.64	$58.65	$58.60
Purchase #7	$220.44	3.361%	$227.849	$227.85	$227.85	$227.80
7 purchase totals =	$776.70		$825.7181	$825.72	$825.75	$825.60