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	$160.70	4.873%	$168.5309	$168.53	$168.55	$168.50
Purchase #2	$196.26	10.654%	$217.1695	$217.17	$217.15	$217.20
Purchase #3	$116.91	10.861%	$129.6076	$129.61	$129.60	$129.60
Purchase #4	$104.32	10.347%	$115.114	$115.11	$115.10	$115.10
Purchase #5	$239.30	4.855%	$250.918	$250.92	$250.90	$250.90
Purchase #6	$81.63	11.316%	$90.8673	$90.87	$90.85	$90.90
Purchase #7	$133.83	5.328%	$140.9605	$140.96	$140.95	$141.00
7 purchase totals =	$1,032.95		$1,113.1678	$1,113.17	$1,113.10	$1,113.20