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	$244.54	4.441%	$255.4	$255.40	$255.40	$255.40
Purchase #2	$71.94	10.138%	$79.2333	$79.23	$79.25	$79.20
Purchase #3	$98.76	5.376%	$104.0693	$104.07	$104.05	$104.10
Purchase #4	$77.64	5.179%	$81.661	$81.66	$81.65	$81.70
Purchase #5	$83.51	3.671%	$86.5757	$86.58	$86.60	$86.60
Purchase #6	$32.33	12.783%	$36.4627	$36.46	$36.45	$36.50
Purchase #7	$144.55	5.196%	$152.0608	$152.06	$152.05	$152.10
7 purchase totals =	$753.27		$795.4628	$795.46	$795.45	$795.60