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	$98.69	5.296%	$103.9166	$103.92	$103.90	$103.90
Purchase #2	$143.40	13.529%	$162.8006	$162.80	$162.80	$162.80
Purchase #3	$43.46	13.327%	$49.2519	$49.25	$49.25	$49.30
Purchase #4	$67.93	5.614%	$71.7436	$71.74	$71.75	$71.70
Purchase #5	$238.90	3.790%	$247.9543	$247.95	$247.95	$248.00
Purchase #6	$176.34	8.398%	$191.149	$191.15	$191.15	$191.10
Purchase #7	$115.70	6.590%	$123.3246	$123.32	$123.30	$123.30
7 purchase totals =	$884.42		$950.1406	$950.13	$950.10	$950.10