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	$78.33	5.138%	$82.3546	$82.35	$82.35	$82.40
Purchase #2	$93.76	9.391%	$102.565	$102.57	$102.55	$102.60
Purchase #3	$85.86	5.404%	$90.4999	$90.50	$90.50	$90.50
Purchase #4	$145.91	12.853%	$164.6638	$164.66	$164.65	$164.70
Purchase #5	$158.31	8.722%	$172.1178	$172.12	$172.10	$172.10
Purchase #6	$6.45	4.402%	$6.7339	$6.73	$6.75	$6.70
Purchase #7	$96.99	11.328%	$107.977	$107.98	$108.00	$108.00
7 purchase totals =	$665.61		$726.9120	$726.91	$726.90	$727.00