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	$210.89	13.240%	$238.8118	$238.81	$238.80	$238.80
Purchase #2	$49.65	10.372%	$54.7997	$54.80	$54.80	$54.80
Purchase #3	$91.95	6.760%	$98.1658	$98.17	$98.15	$98.20
Purchase #4	$167.34	12.216%	$187.7823	$187.78	$187.80	$187.80
Purchase #5	$78.64	13.795%	$89.4884	$89.49	$89.50	$89.50
Purchase #6	$131.96	3.856%	$137.0484	$137.05	$137.05	$137.00
Purchase #7	$206.59	12.279%	$231.9572	$231.96	$231.95	$232.00
7 purchase totals =	$937.02		$1,038.0536	$1,038.06	$1,038.05	$1,038.10