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	$123.36	3.480%	$127.6529	$127.65	$127.65	$127.70
Purchase #2	$73.29	12.551%	$82.4886	$82.49	$82.50	$82.50
Purchase #3	$67.38	6.715%	$71.9046	$71.90	$71.90	$71.90
Purchase #4	$145.61	3.263%	$150.3613	$150.36	$150.35	$150.40
Purchase #5	$106.56	7.307%	$114.3463	$114.35	$114.35	$114.30
Purchase #6	$210.79	13.811%	$239.9022	$239.90	$239.90	$239.90
Purchase #7	$134.84	12.177%	$151.2595	$151.26	$151.25	$151.30
7 purchase totals =	$861.83		$937.9154	$937.91	$937.90	$938.00