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	$145.55	6.121%	$154.4591	$154.46	$154.45	$154.50
Purchase #2	$167.80	7.461%	$180.3196	$180.32	$180.30	$180.30
Purchase #3	$234.47	6.174%	$248.9462	$248.95	$248.95	$248.90
Purchase #4	$16.91	11.336%	$18.8269	$18.83	$18.85	$18.80
Purchase #5	$31.26	12.833%	$35.2716	$35.27	$35.25	$35.30
Purchase #6	$167.55	4.115%	$174.4447	$174.44	$174.45	$174.40
Purchase #7	$238.38	4.717%	$249.6244	$249.62	$249.60	$249.60
7 purchase totals =	$1,001.92		$1,061.8925	$1,061.89	$1,061.85	$1,061.80