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	$55.92	11.351%	$62.2675	$62.27	$62.25	$62.30
Purchase #2	$80.61	6.442%	$85.8029	$85.80	$85.80	$85.80
Purchase #3	$127.94	12.689%	$144.1743	$144.17	$144.15	$144.20
Purchase #4	$17.93	6.807%	$19.1505	$19.15	$19.15	$19.20
Purchase #5	$168.85	3.807%	$175.2781	$175.28	$175.30	$175.30
Purchase #6	$59.46	9.739%	$65.2508	$65.25	$65.25	$65.30
Purchase #7	$205.30	7.128%	$219.9338	$219.93	$219.95	$219.90
7 purchase totals =	$716.01		$771.8579	$771.85	$771.85	$772.00