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	$149.78	10.517%	$165.5324	$165.53	$165.55	$165.50
Purchase #2	$165.33	9.695%	$181.3587	$181.36	$181.35	$181.40
Purchase #3	$81.62	10.582%	$90.257	$90.26	$90.25	$90.30
Purchase #4	$179.25	9.670%	$196.5835	$196.58	$196.60	$196.60
Purchase #5	$144.98	4.338%	$151.2692	$151.27	$151.25	$151.30
Purchase #6	$222.50	12.598%	$250.5306	$250.53	$250.55	$250.50
Purchase #7	$245.42	11.303%	$273.1598	$273.16	$273.15	$273.20
7 purchase totals =	$1,188.88		$1,308.6912	$1,308.69	$1,308.70	$1,308.80