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	$174.95	11.414%	$194.9188	$194.92	$194.90	$194.90
Purchase #2	$82.82	9.328%	$90.5454	$90.55	$90.55	$90.50
Purchase #3	$116.59	7.343%	$125.1512	$125.15	$125.15	$125.20
Purchase #4	$114.41	7.286%	$122.7459	$122.75	$122.75	$122.70
Purchase #5	$94.54	11.352%	$105.2722	$105.27	$105.25	$105.30
Purchase #6	$103.62	3.346%	$107.0871	$107.09	$107.10	$107.10
Purchase #7	$82.54	8.460%	$89.5229	$89.52	$89.50	$89.50
7 purchase totals =	$769.47		$835.2435	$835.25	$835.20	$835.20