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	$105.84	7.115%	$113.3705	$113.37	$113.35	$113.40
Purchase #2	$42.99	10.504%	$47.5057	$47.51	$47.50	$47.50
Purchase #3	$246.91	4.673%	$258.4481	$258.45	$258.45	$258.40
Purchase #4	$109.36	7.277%	$117.3181	$117.32	$117.30	$117.30
Purchase #5	$214.91	9.118%	$234.5055	$234.51	$234.50	$234.50
Purchase #6	$187.87	11.702%	$209.8545	$209.85	$209.85	$209.90
Purchase #7	$174.88	9.526%	$191.5391	$191.54	$191.55	$191.50
7 purchase totals =	$1,082.76		$1,172.5415	$1,172.55	$1,172.50	$1,172.50