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	$99.28	13.638%	$112.8198	$112.82	$112.80	$112.80
Purchase #2	$64.50	10.735%	$71.4241	$71.42	$71.40	$71.40
Purchase #3	$120.80	4.171%	$125.8386	$125.84	$125.85	$125.80
Purchase #4	$62.77	3.359%	$64.8784	$64.88	$64.90	$64.90
Purchase #5	$116.66	12.346%	$131.0628	$131.06	$131.05	$131.10
Purchase #6	$180.37	7.565%	$194.015	$194.02	$194.00	$194.00
Purchase #7	$96.43	9.252%	$105.3517	$105.35	$105.35	$105.40
7 purchase totals =	$740.81		$805.3904	$805.39	$805.35	$805.40