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	$56.59	5.374%	$59.6311	$59.63	$59.65	$59.60
Purchase #2	$98.41	3.167%	$101.5266	$101.53	$101.55	$101.50
Purchase #3	$203.31	3.606%	$210.6414	$210.64	$210.65	$210.60
Purchase #4	$134.46	5.688%	$142.1081	$142.11	$142.10	$142.10
Purchase #5	$76.42	4.418%	$79.7962	$79.80	$79.80	$79.80
Purchase #6	$80.27	12.278%	$90.1256	$90.13	$90.15	$90.10
Purchase #7	$241.44	8.264%	$261.3926	$261.39	$261.40	$261.40
7 purchase totals =	$890.90		$945.2216	$945.23	$945.30	$945.10