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	$221.32	8.647%	$240.4575	$240.46	$240.45	$240.50
Purchase #2	$214.49	5.700%	$226.7159	$226.72	$226.70	$226.70
Purchase #3	$81.87	6.575%	$87.253	$87.25	$87.25	$87.30
Purchase #4	$150.58	5.331%	$158.6074	$158.61	$158.60	$158.60
Purchase #5	$210.73	11.711%	$235.4086	$235.41	$235.40	$235.40
Purchase #6	$88.56	9.371%	$96.859	$96.86	$96.85	$96.90
Purchase #7	$40.79	12.605%	$45.9316	$45.93	$45.95	$45.90
7 purchase totals =	$1,008.34		$1,091.2330	$1,091.24	$1,091.20	$1,091.30