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	$176.58	9.132%	$192.7053	$192.71	$192.70	$192.70
Purchase #2	$95.42	10.665%	$105.5965	$105.60	$105.60	$105.60
Purchase #3	$170.88	8.454%	$185.3262	$185.33	$185.35	$185.30
Purchase #4	$45.25	11.373%	$50.3963	$50.40	$50.40	$50.40
Purchase #5	$182.69	6.154%	$193.9327	$193.93	$193.95	$193.90
Purchase #6	$82.58	9.349%	$90.3004	$90.30	$90.30	$90.30
Purchase #7	$190.67	4.433%	$199.1224	$199.12	$199.10	$199.10
7 purchase totals =	$944.07		$1,017.3798	$1,017.39	$1,017.40	$1,017.30