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	$149.85	11.405%	$166.9404	$166.94	$166.95	$166.90
Purchase #2	$189.35	5.404%	$199.5825	$199.58	$199.60	$199.60
Purchase #3	$91.38	12.749%	$103.03	$103.03	$103.05	$103.00
Purchase #4	$10.53	12.809%	$11.8788	$11.88	$11.90	$11.90
Purchase #5	$174.26	4.318%	$181.7845	$181.78	$181.80	$181.80
Purchase #6	$104.49	5.241%	$109.9663	$109.97	$109.95	$110.00
Purchase #7	$62.81	13.529%	$71.3076	$71.31	$71.30	$71.30
7 purchase totals =	$782.67		$844.4901	$844.49	$844.55	$844.50