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	$171.29	8.479%	$185.8137	$185.81	$185.80	$185.80
Purchase #2	$167.69	12.232%	$188.2018	$188.20	$188.20	$188.20
Purchase #3	$24.45	5.356%	$25.7595	$25.76	$25.75	$25.80
Purchase #4	$142.25	3.185%	$146.7807	$146.78	$146.80	$146.80
Purchase #5	$211.38	3.758%	$219.3237	$219.32	$219.30	$219.30
Purchase #6	$163.29	11.329%	$181.7891	$181.79	$181.80	$181.80
Purchase #7	$69.94	12.861%	$78.935	$78.94	$78.95	$78.90
7 purchase totals =	$950.29		$1,026.6035	$1,026.60	$1,026.60	$1,026.60