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	$103.78	11.661%	$115.8818	$115.88	$115.90	$115.90
Purchase #2	$175.85	3.597%	$182.1753	$182.18	$182.20	$182.20
Purchase #3	$158.36	13.551%	$179.8194	$179.82	$179.80	$179.80
Purchase #4	$231.45	12.112%	$259.4832	$259.48	$259.50	$259.50
Purchase #5	$188.81	12.336%	$212.1016	$212.10	$212.10	$212.10
Purchase #6	$79.56	4.721%	$83.316	$83.32	$83.30	$83.30
Purchase #7	$41.74	9.408%	$45.6669	$45.67	$45.65	$45.70
7 purchase totals =	$979.55		$1,078.4442	$1,078.45	$1,078.45	$1,078.50