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	$160.99	9.396%	$176.1166	$176.12	$176.10	$176.10
Purchase #2	$140.95	3.124%	$145.3533	$145.35	$145.35	$145.40
Purchase #3	$129.91	11.519%	$144.8743	$144.87	$144.85	$144.90
Purchase #4	$143.43	6.573%	$152.8577	$152.86	$152.85	$152.90
Purchase #5	$239.34	4.752%	$250.7134	$250.71	$250.70	$250.70
Purchase #6	$83.45	10.147%	$91.9177	$91.92	$91.90	$91.90
Purchase #7	$126.48	12.604%	$142.4215	$142.42	$142.40	$142.40
7 purchase totals =	$1,024.55		$1,104.2545	$1,104.25	$1,104.15	$1,104.30