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	$65.87	5.839%	$69.7161	$69.72	$69.70	$69.70
Purchase #2	$30.51	3.529%	$31.5867	$31.59	$31.60	$31.60
Purchase #3	$221.41	13.196%	$250.6273	$250.63	$250.65	$250.60
Purchase #4	$142.60	5.411%	$150.3161	$150.32	$150.30	$150.30
Purchase #5	$161.36	6.113%	$171.2239	$171.22	$171.20	$171.20
Purchase #6	$232.59	7.266%	$249.49	$249.49	$249.50	$249.50
Purchase #7	$10.52	9.515%	$11.521	$11.52	$11.50	$11.50
7 purchase totals =	$864.86		$934.4811	$934.49	$934.45	$934.40