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	$110.90	11.116%	$123.2276	$123.23	$123.25	$123.20
Purchase #2	$101.26	9.807%	$111.1906	$111.19	$111.20	$111.20
Purchase #3	$66.94	7.630%	$72.0475	$72.05	$72.05	$72.00
Purchase #4	$105.43	9.188%	$115.1169	$115.12	$115.10	$115.10
Purchase #5	$74.50	10.121%	$82.0401	$82.04	$82.05	$82.00
Purchase #6	$175.47	6.736%	$187.2897	$187.29	$187.30	$187.30
Purchase #7	$87.81	11.211%	$97.6544	$97.65	$97.65	$97.70
7 purchase totals =	$722.31		$788.5668	$788.57	$788.60	$788.50