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	$164.64	6.592%	$175.4931	$175.49	$175.50	$175.50
Purchase #2	$168.58	9.870%	$185.2188	$185.22	$185.20	$185.20
Purchase #3	$56.75	4.550%	$59.3321	$59.33	$59.35	$59.30
Purchase #4	$163.95	10.501%	$181.1664	$181.17	$181.15	$181.20
Purchase #5	$164.81	4.587%	$172.3698	$172.37	$172.35	$172.40
Purchase #6	$197.36	13.334%	$223.676	$223.68	$223.70	$223.70
Purchase #7	$105.98	9.720%	$116.2813	$116.28	$116.30	$116.30
7 purchase totals =	$1,022.07		$1,113.5375	$1,113.54	$1,113.55	$1,113.60