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	$98.36	8.201%	$106.4265	$106.43	$106.45	$106.40
Purchase #2	$90.91	9.146%	$99.2246	$99.22	$99.20	$99.20
Purchase #3	$213.45	6.127%	$226.5281	$226.53	$226.55	$226.50
Purchase #4	$118.52	11.214%	$131.8108	$131.81	$131.80	$131.80
Purchase #5	$185.69	13.382%	$210.539	$210.54	$210.55	$210.50
Purchase #6	$103.41	12.681%	$116.5234	$116.52	$116.50	$116.50
Purchase #7	$173.31	4.144%	$180.492	$180.49	$180.50	$180.50
7 purchase totals =	$983.65		$1,071.5444	$1,071.54	$1,071.55	$1,071.40