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	$48.44	9.147%	$52.8708	$52.87	$52.85	$52.90
Purchase #2	$199.55	7.656%	$214.8275	$214.83	$214.85	$214.80
Purchase #3	$196.85	11.558%	$219.6019	$219.60	$219.60	$219.60
Purchase #4	$47.54	12.795%	$53.6227	$53.62	$53.60	$53.60
Purchase #5	$133.37	13.132%	$150.8841	$150.88	$150.90	$150.90
Purchase #6	$22.84	10.841%	$25.3161	$25.32	$25.30	$25.30
Purchase #7	$194.27	7.372%	$208.5916	$208.59	$208.60	$208.60
7 purchase totals =	$842.86		$925.7147	$925.71	$925.70	$925.70