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	$93.69	12.415%	$105.3216	$105.32	$105.30	$105.30
Purchase #2	$145.45	13.370%	$164.8967	$164.90	$164.90	$164.90
Purchase #3	$182.37	9.123%	$199.0076	$199.01	$199.00	$199.00
Purchase #4	$168.33	8.413%	$182.4916	$182.49	$182.50	$182.50
Purchase #5	$191.59	12.752%	$216.0216	$216.02	$216.00	$216.00
Purchase #6	$230.69	8.386%	$250.0357	$250.04	$250.05	$250.00
Purchase #7	$170.38	5.416%	$179.6078	$179.61	$179.60	$179.60
7 purchase totals =	$1,182.50		$1,297.3826	$1,297.39	$1,297.35	$1,297.30