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	$35.96	3.588%	$37.2502	$37.25	$37.25	$37.30
Purchase #2	$242.97	9.800%	$266.7811	$266.78	$266.80	$266.80
Purchase #3	$226.70	7.296%	$243.24	$243.24	$243.25	$243.20
Purchase #4	$105.60	13.370%	$119.7187	$119.72	$119.70	$119.70
Purchase #5	$80.41	11.356%	$89.5414	$89.54	$89.55	$89.50
Purchase #6	$198.67	5.150%	$208.9015	$208.90	$208.90	$208.90
Purchase #7	$170.56	12.136%	$191.2592	$191.26	$191.25	$191.30
7 purchase totals =	$1,060.87		$1,156.6921	$1,156.69	$1,156.70	$1,156.70