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	$205.98	4.514%	$215.2779	$215.28	$215.30	$215.30
Purchase #2	$24.71	4.847%	$25.9077	$25.91	$25.90	$25.90
Purchase #3	$160.36	4.252%	$167.1785	$167.18	$167.20	$167.20
Purchase #4	$34.72	11.213%	$38.6132	$38.61	$38.60	$38.60
Purchase #5	$180.38	9.142%	$196.8703	$196.87	$196.85	$196.90
Purchase #6	$94.82	3.729%	$98.3558	$98.36	$98.35	$98.40
Purchase #7	$165.91	9.846%	$182.2455	$182.25	$182.25	$182.20
7 purchase totals =	$866.88		$924.4489	$924.46	$924.45	$924.50