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	$123.66	13.473%	$140.3207	$140.32	$140.30	$140.30
Purchase #2	$85.74	7.523%	$92.1902	$92.19	$92.20	$92.20
Purchase #3	$229.38	12.105%	$257.1464	$257.15	$257.15	$257.10
Purchase #4	$93.55	9.156%	$102.1154	$102.12	$102.10	$102.10
Purchase #5	$189.48	13.641%	$215.327	$215.33	$215.35	$215.30
Purchase #6	$189.66	3.731%	$196.7362	$196.74	$196.75	$196.70
Purchase #7	$134.72	5.628%	$142.302	$142.30	$142.30	$142.30
7 purchase totals =	$1,046.19		$1,146.1379	$1,146.15	$1,146.15	$1,146.00