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	$97.68	10.190%	$107.6336	$107.63	$107.65	$107.60
Purchase #2	$213.97	13.789%	$243.4743	$243.47	$243.45	$243.50
Purchase #3	$192.56	12.352%	$216.345	$216.35	$216.35	$216.30
Purchase #4	$53.88	10.314%	$59.4372	$59.44	$59.45	$59.40
Purchase #5	$51.51	6.250%	$54.7294	$54.73	$54.75	$54.70
Purchase #6	$154.31	3.250%	$159.3251	$159.33	$159.35	$159.30
Purchase #7	$220.34	10.707%	$243.9318	$243.93	$243.95	$243.90
7 purchase totals =	$984.25		$1,084.8764	$1,084.88	$1,084.95	$1,084.70