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	$48.46	10.793%	$53.6903	$53.69	$53.70	$53.70
Purchase #2	$69.94	12.461%	$78.6552	$78.66	$78.65	$78.70
Purchase #3	$6.83	4.717%	$7.1522	$7.15	$7.15	$7.20
Purchase #4	$250.50	7.792%	$270.019	$270.02	$270.00	$270.00
Purchase #5	$24.33	11.705%	$27.1778	$27.18	$27.20	$27.20
Purchase #6	$111.30	3.105%	$114.7559	$114.76	$114.75	$114.80
Purchase #7	$108.69	8.233%	$117.6384	$117.64	$117.65	$117.60
7 purchase totals =	$620.05		$669.0888	$669.10	$669.10	$669.20