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	$116.33	9.344%	$127.1999	$127.20	$127.20	$127.20
Purchase #2	$183.28	10.737%	$202.9588	$202.96	$202.95	$203.00
Purchase #3	$75.30	4.334%	$78.5635	$78.56	$78.55	$78.60
Purchase #4	$13.66	9.469%	$14.9535	$14.95	$14.95	$15.00
Purchase #5	$66.92	8.272%	$72.4556	$72.46	$72.45	$72.50
Purchase #6	$67.84	5.479%	$71.557	$71.56	$71.55	$71.60
Purchase #7	$101.63	3.692%	$105.3822	$105.38	$105.40	$105.40
7 purchase totals =	$624.96		$673.0705	$673.07	$673.05	$673.30