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	$159.67	4.798%	$167.331	$167.33	$167.35	$167.30
Purchase #2	$70.38	11.479%	$78.4589	$78.46	$78.45	$78.50
Purchase #3	$234.86	7.593%	$252.6929	$252.69	$252.70	$252.70
Purchase #4	$181.57	12.409%	$204.101	$204.10	$204.10	$204.10
Purchase #5	$70.72	11.651%	$78.9596	$78.96	$78.95	$79.00
Purchase #6	$23.30	8.704%	$25.328	$25.33	$25.35	$25.30
Purchase #7	$60.46	8.482%	$65.5882	$65.59	$65.60	$65.60
7 purchase totals =	$800.96		$872.4596	$872.46	$872.50	$872.50