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	$120.72	5.520%	$127.3837	$127.38	$127.40	$127.40
Purchase #2	$222.65	8.689%	$241.9961	$242.00	$242.00	$242.00
Purchase #3	$39.96	11.398%	$44.5146	$44.51	$44.50	$44.50
Purchase #4	$143.78	12.773%	$162.145	$162.15	$162.15	$162.10
Purchase #5	$108.35	5.827%	$114.6636	$114.66	$114.65	$114.70
Purchase #6	$214.59	11.334%	$238.9116	$238.91	$238.90	$238.90
Purchase #7	$159.58	3.864%	$165.7462	$165.75	$165.75	$165.70
7 purchase totals =	$1,009.63		$1,095.3608	$1,095.36	$1,095.35	$1,095.30