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	$38.30	8.234%	$41.4536	$41.45	$41.45	$41.50
Purchase #2	$158.51	8.342%	$171.7329	$171.73	$171.75	$171.70
Purchase #3	$179.31	7.799%	$193.2944	$193.29	$193.30	$193.30
Purchase #4	$49.51	3.551%	$51.2681	$51.27	$51.25	$51.30
Purchase #5	$71.70	10.705%	$79.3755	$79.38	$79.40	$79.40
Purchase #6	$78.53	13.661%	$89.258	$89.26	$89.25	$89.30
Purchase #7	$123.94	13.370%	$140.5108	$140.51	$140.50	$140.50
7 purchase totals =	$699.80		$766.8933	$766.89	$766.90	$767.00