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	$174.55	12.343%	$196.0947	$196.09	$196.10	$196.10
Purchase #2	$78.59	8.663%	$85.3983	$85.40	$85.40	$85.40
Purchase #3	$86.64	5.743%	$91.6157	$91.62	$91.60	$91.60
Purchase #4	$225.85	4.206%	$235.3493	$235.35	$235.35	$235.30
Purchase #5	$224.76	8.728%	$244.3771	$244.38	$244.40	$244.40
Purchase #6	$182.60	4.290%	$190.4335	$190.43	$190.45	$190.40
Purchase #7	$166.57	13.384%	$188.8637	$188.86	$188.85	$188.90
7 purchase totals =	$1,139.56		$1,232.1323	$1,232.13	$1,232.15	$1,232.10