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	$161.36	12.229%	$181.0927	$181.09	$181.10	$181.10
Purchase #2	$49.25	5.407%	$51.9129	$51.91	$51.90	$51.90
Purchase #3	$144.63	7.458%	$155.4165	$155.42	$155.40	$155.40
Purchase #4	$61.84	5.238%	$65.0792	$65.08	$65.10	$65.10
Purchase #5	$170.35	11.348%	$189.6813	$189.68	$189.70	$189.70
Purchase #6	$98.57	13.383%	$111.7616	$111.76	$111.75	$111.80
Purchase #7	$83.32	11.474%	$92.8801	$92.88	$92.90	$92.90
7 purchase totals =	$769.32		$847.8243	$847.82	$847.85	$847.90