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	$184.72	5.159%	$194.2497	$194.25	$194.25	$194.20
Purchase #2	$232.69	10.154%	$256.3173	$256.32	$256.30	$256.30
Purchase #3	$111.35	6.143%	$118.1902	$118.19	$118.20	$118.20
Purchase #4	$150.80	12.448%	$169.5716	$169.57	$169.55	$169.60
Purchase #5	$64.41	12.180%	$72.2551	$72.26	$72.25	$72.30
Purchase #6	$111.82	3.256%	$115.4609	$115.46	$115.45	$115.50
Purchase #7	$211.58	13.833%	$240.8479	$240.85	$240.85	$240.80
7 purchase totals =	$1,067.37		$1,166.8927	$1,166.90	$1,166.85	$1,166.90