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	$220.73	6.811%	$235.7639	$235.76	$235.75	$235.80
Purchase #2	$213.34	5.311%	$224.6705	$224.67	$224.65	$224.70
Purchase #3	$127.64	11.621%	$142.473	$142.47	$142.45	$142.50
Purchase #4	$118.35	4.358%	$123.5077	$123.51	$123.50	$123.50
Purchase #5	$231.90	3.193%	$239.3046	$239.30	$239.30	$239.30
Purchase #6	$130.44	8.443%	$141.453	$141.45	$141.45	$141.50
Purchase #7	$60.93	11.366%	$67.8553	$67.86	$67.85	$67.90
7 purchase totals =	$1,103.33		$1,175.0280	$1,175.02	$1,174.95	$1,175.20