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	$209.46	9.283%	$228.9042	$228.90	$228.90	$228.90
Purchase #2	$231.55	4.482%	$241.9281	$241.93	$241.95	$241.90
Purchase #3	$162.49	10.672%	$179.8309	$179.83	$179.85	$179.80
Purchase #4	$154.95	8.252%	$167.7365	$167.74	$167.75	$167.70
Purchase #5	$38.69	4.735%	$40.522	$40.52	$40.50	$40.50
Purchase #6	$162.61	10.790%	$180.1556	$180.16	$180.15	$180.20
Purchase #7	$51.72	8.172%	$55.9466	$55.95	$55.95	$55.90
7 purchase totals =	$1,011.47		$1,095.0239	$1,095.03	$1,095.05	$1,094.90