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	$22.87	11.465%	$25.492	$25.49	$25.50	$25.50
Purchase #2	$28.97	12.641%	$32.6321	$32.63	$32.65	$32.60
Purchase #3	$173.86	12.125%	$194.9405	$194.94	$194.95	$194.90
Purchase #4	$127.77	9.262%	$139.6041	$139.60	$139.60	$139.60
Purchase #5	$243.56	5.461%	$256.8608	$256.86	$256.85	$256.90
Purchase #6	$195.95	12.407%	$220.2615	$220.26	$220.25	$220.30
Purchase #7	$142.29	7.463%	$152.9091	$152.91	$152.90	$152.90
7 purchase totals =	$935.27		$1,022.7001	$1,022.69	$1,022.70	$1,022.70