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	$142.44	6.193%	$151.2613	$151.26	$151.25	$151.30
Purchase #2	$98.71	13.337%	$111.875	$111.88	$111.90	$111.90
Purchase #3	$57.53	13.758%	$65.445	$65.45	$65.45	$65.40
Purchase #4	$203.88	4.474%	$213.0016	$213.00	$213.00	$213.00
Purchase #5	$57.86	13.357%	$65.5884	$65.59	$65.60	$65.60
Purchase #6	$134.77	6.335%	$143.3077	$143.31	$143.30	$143.30
Purchase #7	$194.64	4.446%	$203.2937	$203.29	$203.30	$203.30
7 purchase totals =	$889.83		$953.7727	$953.78	$953.80	$953.80