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	$237.50	10.851%	$263.2711	$263.27	$263.25	$263.30
Purchase #2	$165.67	3.544%	$171.5413	$171.54	$171.55	$171.50
Purchase #3	$119.43	6.641%	$127.3613	$127.36	$127.35	$127.40
Purchase #4	$28.43	11.321%	$31.6486	$31.65	$31.65	$31.60
Purchase #5	$199.34	11.314%	$221.8933	$221.89	$221.90	$221.90
Purchase #6	$12.55	8.587%	$13.6277	$13.63	$13.65	$13.60
Purchase #7	$136.41	6.784%	$145.6641	$145.66	$145.65	$145.70
7 purchase totals =	$899.33		$975.0074	$975.00	$975.00	$975.00