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	$189.92	11.759%	$212.2527	$212.25	$212.25	$212.30
Purchase #2	$161.93	8.322%	$175.4058	$175.41	$175.40	$175.40
Purchase #3	$205.96	4.559%	$215.3497	$215.35	$215.35	$215.30
Purchase #4	$134.99	5.792%	$142.8086	$142.81	$142.80	$142.80
Purchase #5	$240.79	6.505%	$256.4534	$256.45	$256.45	$256.50
Purchase #6	$102.32	9.276%	$111.8112	$111.81	$111.80	$111.80
Purchase #7	$67.49	7.711%	$72.6942	$72.69	$72.70	$72.70
7 purchase totals =	$1,103.40		$1,186.7756	$1,186.77	$1,186.75	$1,186.80