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	$105.51	12.578%	$118.781	$118.78	$118.80	$118.80
Purchase #2	$102.72	3.164%	$105.9701	$105.97	$105.95	$106.00
Purchase #3	$239.32	11.272%	$266.2962	$266.30	$266.30	$266.30
Purchase #4	$50.56	5.303%	$53.2412	$53.24	$53.25	$53.20
Purchase #5	$163.25	3.713%	$169.3115	$169.31	$169.30	$169.30
Purchase #6	$57.59	9.365%	$62.9833	$62.98	$63.00	$63.00
Purchase #7	$216.54	11.596%	$241.65	$241.65	$241.65	$241.70
7 purchase totals =	$935.49		$1,018.2333	$1,018.23	$1,018.25	$1,018.30