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	$147.94	9.639%	$162.1999	$162.20	$162.20	$162.20
Purchase #2	$53.51	4.815%	$56.0865	$56.09	$56.10	$56.10
Purchase #3	$181.58	8.337%	$196.7183	$196.72	$196.70	$196.70
Purchase #4	$114.43	11.445%	$127.5265	$127.53	$127.55	$127.50
Purchase #5	$75.25	9.541%	$82.4296	$82.43	$82.45	$82.40
Purchase #6	$155.96	12.743%	$175.834	$175.83	$175.85	$175.80
Purchase #7	$79.44	11.776%	$88.7949	$88.79	$88.80	$88.80
7 purchase totals =	$808.11		$889.5897	$889.59	$889.65	$889.50