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	$229.33	12.244%	$257.4092	$257.41	$257.40	$257.40
Purchase #2	$115.38	10.667%	$127.6876	$127.69	$127.70	$127.70
Purchase #3	$174.41	10.179%	$192.1632	$192.16	$192.15	$192.20
Purchase #4	$148.38	8.461%	$160.9344	$160.93	$160.95	$160.90
Purchase #5	$110.30	4.190%	$114.9216	$114.92	$114.90	$114.90
Purchase #6	$98.35	5.345%	$103.6068	$103.61	$103.60	$103.60
Purchase #7	$230.68	3.416%	$238.56	$238.56	$238.55	$238.60
7 purchase totals =	$1,106.83		$1,195.2828	$1,195.28	$1,195.25	$1,195.30