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	$34.54	11.288%	$38.4389	$38.44	$38.45	$38.40
Purchase #2	$86.92	10.332%	$95.9006	$95.90	$95.90	$95.90
Purchase #3	$73.99	11.567%	$82.5484	$82.55	$82.55	$82.50
Purchase #4	$240.34	4.113%	$250.2252	$250.23	$250.25	$250.20
Purchase #5	$100.62	7.558%	$108.2249	$108.22	$108.20	$108.20
Purchase #6	$213.90	13.820%	$243.461	$243.46	$243.45	$243.50
Purchase #7	$173.52	9.338%	$189.7233	$189.72	$189.70	$189.70
7 purchase totals =	$923.83		$1,008.5223	$1,008.52	$1,008.50	$1,008.40