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	$49.98	5.569%	$52.7634	$52.76	$52.75	$52.80
Purchase #2	$57.27	7.546%	$61.5916	$61.59	$61.60	$61.60
Purchase #3	$226.94	10.679%	$251.1749	$251.17	$251.15	$251.20
Purchase #4	$229.99	11.191%	$255.7282	$255.73	$255.75	$255.70
Purchase #5	$84.74	6.552%	$90.2922	$90.29	$90.30	$90.30
Purchase #6	$215.96	4.653%	$226.0086	$226.01	$226.00	$226.00
Purchase #7	$128.55	9.429%	$140.671	$140.67	$140.65	$140.70
7 purchase totals =	$993.43		$1,078.2299	$1,078.22	$1,078.20	$1,078.30