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	$76.72	11.808%	$85.7791	$85.78	$85.80	$85.80
Purchase #2	$77.40	4.561%	$80.9302	$80.93	$80.95	$80.90
Purchase #3	$170.47	10.462%	$188.3046	$188.30	$188.30	$188.30
Purchase #4	$112.89	4.333%	$117.7815	$117.78	$117.80	$117.80
Purchase #5	$82.34	9.569%	$90.2191	$90.22	$90.20	$90.20
Purchase #6	$188.58	8.585%	$204.7696	$204.77	$204.75	$204.80
Purchase #7	$246.46	6.179%	$261.6888	$261.69	$261.70	$261.70
7 purchase totals =	$954.86		$1,029.4729	$1,029.47	$1,029.50	$1,029.50