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	$187.38	6.568%	$199.6871	$199.69	$199.70	$199.70
Purchase #2	$64.93	12.315%	$72.9261	$72.93	$72.95	$72.90
Purchase #3	$53.41	7.586%	$57.4617	$57.46	$57.45	$57.50
Purchase #4	$28.96	13.619%	$32.9041	$32.90	$32.90	$32.90
Purchase #5	$175.33	3.280%	$181.0808	$181.08	$181.10	$181.10
Purchase #6	$159.25	7.692%	$171.4995	$171.50	$171.50	$171.50
Purchase #7	$197.44	4.144%	$205.6219	$205.62	$205.60	$205.60
7 purchase totals =	$866.70		$921.1812	$921.18	$921.20	$921.20