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	$219.50	10.478%	$242.4992	$242.50	$242.50	$242.50
Purchase #2	$71.93	10.394%	$79.4064	$79.41	$79.40	$79.40
Purchase #3	$250.45	4.819%	$262.5192	$262.52	$262.50	$262.50
Purchase #4	$167.91	6.260%	$178.4212	$178.42	$178.40	$178.40
Purchase #5	$16.57	6.596%	$17.663	$17.66	$17.65	$17.70
Purchase #6	$75.82	13.327%	$85.9245	$85.92	$85.90	$85.90
Purchase #7	$152.27	6.473%	$162.1264	$162.13	$162.15	$162.10
7 purchase totals =	$954.45		$1,028.5599	$1,028.56	$1,028.50	$1,028.50