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	$175.79	5.164%	$184.8678	$184.87	$184.85	$184.90
Purchase #2	$70.79	10.753%	$78.402	$78.40	$78.40	$78.40
Purchase #3	$71.27	6.457%	$75.8719	$75.87	$75.85	$75.90
Purchase #4	$101.41	13.732%	$115.3356	$115.34	$115.35	$115.30
Purchase #5	$207.57	7.244%	$222.6064	$222.61	$222.60	$222.60
Purchase #6	$37.65	9.794%	$41.3374	$41.34	$41.35	$41.30
Purchase #7	$152.61	9.535%	$167.1614	$167.16	$167.15	$167.20
7 purchase totals =	$817.09		$885.5825	$885.59	$885.55	$885.60