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	$63.68	10.606%	$70.4339	$70.43	$70.45	$70.40
Purchase #2	$154.56	6.676%	$164.8784	$164.88	$164.90	$164.90
Purchase #3	$190.41	8.347%	$206.3035	$206.30	$206.30	$206.30
Purchase #4	$128.41	10.325%	$141.6683	$141.67	$141.65	$141.70
Purchase #5	$154.27	9.118%	$168.3363	$168.34	$168.35	$168.30
Purchase #6	$113.95	11.656%	$127.232	$127.23	$127.25	$127.20
Purchase #7	$207.45	12.102%	$232.5556	$232.56	$232.55	$232.60
7 purchase totals =	$1,012.73		$1,111.4080	$1,111.41	$1,111.45	$1,111.40