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	$174.50	3.680%	$180.9216	$180.92	$180.90	$180.90
Purchase #2	$229.96	3.341%	$237.643	$237.64	$237.65	$237.60
Purchase #3	$38.59	11.492%	$43.0248	$43.02	$43.00	$43.00
Purchase #4	$90.47	11.236%	$100.6352	$100.64	$100.65	$100.60
Purchase #5	$154.46	12.728%	$174.1197	$174.12	$174.10	$174.10
Purchase #6	$95.55	8.373%	$103.5504	$103.55	$103.55	$103.60
Purchase #7	$101.82	6.722%	$108.6643	$108.66	$108.65	$108.70
7 purchase totals =	$885.35		$948.5590	$948.55	$948.50	$948.50