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	$82.88	11.178%	$92.1443	$92.14	$92.15	$92.10
Purchase #2	$200.39	4.568%	$209.5438	$209.54	$209.55	$209.50
Purchase #3	$163.31	11.110%	$181.4537	$181.45	$181.45	$181.50
Purchase #4	$157.77	5.728%	$166.8071	$166.81	$166.80	$166.80
Purchase #5	$99.67	9.805%	$109.4426	$109.44	$109.45	$109.40
Purchase #6	$170.43	4.408%	$177.9426	$177.94	$177.95	$177.90
Purchase #7	$75.88	12.458%	$85.3331	$85.33	$85.35	$85.30
7 purchase totals =	$950.33		$1,022.6672	$1,022.65	$1,022.70	$1,022.50