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	$203.35	5.855%	$215.2561	$215.26	$215.25	$215.30
Purchase #2	$207.77	9.689%	$227.9008	$227.90	$227.90	$227.90
Purchase #3	$94.88	4.629%	$99.272	$99.27	$99.25	$99.30
Purchase #4	$84.25	7.755%	$90.7836	$90.78	$90.80	$90.80
Purchase #5	$225.27	3.802%	$233.8348	$233.83	$233.85	$233.80
Purchase #6	$203.56	12.561%	$229.1292	$229.13	$229.15	$229.10
Purchase #7	$71.99	8.469%	$78.0868	$78.09	$78.10	$78.10
7 purchase totals =	$1,091.07		$1,174.2633	$1,174.26	$1,174.30	$1,174.30