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	$96.32	13.661%	$109.4783	$109.48	$109.50	$109.50
Purchase #2	$174.86	13.437%	$198.3559	$198.36	$198.35	$198.40
Purchase #3	$69.72	8.724%	$75.8024	$75.80	$75.80	$75.80
Purchase #4	$240.88	7.312%	$258.4931	$258.49	$258.50	$258.50
Purchase #5	$72.92	10.589%	$80.6415	$80.64	$80.65	$80.60
Purchase #6	$188.73	11.647%	$210.7114	$210.71	$210.70	$210.70
Purchase #7	$96.93	9.271%	$105.9164	$105.92	$105.90	$105.90
7 purchase totals =	$940.36		$1,039.3990	$1,039.40	$1,039.40	$1,039.40