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	$170.57	8.493%	$185.0565	$185.06	$185.05	$185.10
Purchase #2	$136.39	8.312%	$147.7267	$147.73	$147.75	$147.70
Purchase #3	$75.72	9.284%	$82.7498	$82.75	$82.75	$82.70
Purchase #4	$163.72	11.689%	$182.8572	$182.86	$182.85	$182.90
Purchase #5	$198.55	7.840%	$214.1163	$214.12	$214.10	$214.10
Purchase #6	$192.26	4.390%	$200.7002	$200.70	$200.70	$200.70
Purchase #7	$34.72	10.233%	$38.2729	$38.27	$38.25	$38.30
7 purchase totals =	$971.93		$1,051.4796	$1,051.49	$1,051.45	$1,051.50