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	$195.35	10.801%	$216.4498	$216.45	$216.45	$216.40
Purchase #2	$70.49	13.668%	$80.1246	$80.12	$80.10	$80.10
Purchase #3	$221.43	12.219%	$248.4865	$248.49	$248.50	$248.50
Purchase #4	$189.81	9.822%	$208.4531	$208.45	$208.45	$208.50
Purchase #5	$65.73	3.291%	$67.8932	$67.89	$67.90	$67.90
Purchase #6	$52.84	10.641%	$58.4627	$58.46	$58.45	$58.50
Purchase #7	$164.51	4.279%	$171.5494	$171.55	$171.55	$171.50
7 purchase totals =	$960.16		$1,051.4193	$1,051.41	$1,051.40	$1,051.40