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	$45.59	4.692%	$47.7291	$47.73	$47.75	$47.70
Purchase #2	$230.71	8.293%	$249.8428	$249.84	$249.85	$249.80
Purchase #3	$89.57	10.572%	$99.0393	$99.04	$99.05	$99.00
Purchase #4	$108.58	4.626%	$113.6029	$113.60	$113.60	$113.60
Purchase #5	$180.32	5.596%	$190.4107	$190.41	$190.40	$190.40
Purchase #6	$242.75	5.421%	$255.9095	$255.91	$255.90	$255.90
Purchase #7	$96.67	9.202%	$105.5656	$105.57	$105.55	$105.60
7 purchase totals =	$994.19		$1,062.0999	$1,062.10	$1,062.10	$1,062.00