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	$130.31	9.654%	$142.8901	$142.89	$142.90	$142.90
Purchase #2	$145.48	13.688%	$165.3933	$165.39	$165.40	$165.40
Purchase #3	$53.93	7.478%	$57.9629	$57.96	$57.95	$58.00
Purchase #4	$244.66	7.397%	$262.7575	$262.76	$262.75	$262.80
Purchase #5	$80.65	7.821%	$86.9576	$86.96	$86.95	$87.00
Purchase #6	$226.99	5.239%	$238.882	$238.88	$238.90	$238.90
Purchase #7	$87.84	5.179%	$92.3892	$92.39	$92.40	$92.40
7 purchase totals =	$969.86		$1,047.2326	$1,047.23	$1,047.25	$1,047.40