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	$237.76	3.286%	$245.5728	$245.57	$245.55	$245.60
Purchase #2	$152.72	8.370%	$165.5027	$165.50	$165.50	$165.50
Purchase #3	$194.67	3.391%	$201.2713	$201.27	$201.25	$201.30
Purchase #4	$78.32	10.678%	$86.683	$86.68	$86.70	$86.70
Purchase #5	$18.60	9.825%	$20.4275	$20.43	$20.45	$20.40
Purchase #6	$150.83	7.589%	$162.2765	$162.28	$162.30	$162.30
Purchase #7	$193.99	7.481%	$208.5024	$208.50	$208.50	$208.50
7 purchase totals =	$1,026.89		$1,090.2362	$1,090.23	$1,090.25	$1,090.30