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	$41.48	7.365%	$44.535	$44.54	$44.55	$44.50
Purchase #2	$40.80	3.702%	$42.3104	$42.31	$42.30	$42.30
Purchase #3	$191.59	9.181%	$209.1799	$209.18	$209.20	$209.20
Purchase #4	$145.77	11.174%	$162.0583	$162.06	$162.05	$162.10
Purchase #5	$83.27	3.641%	$86.3019	$86.30	$86.30	$86.30
Purchase #6	$147.27	5.558%	$155.4553	$155.46	$155.45	$155.50
Purchase #7	$172.65	6.623%	$184.0846	$184.08	$184.10	$184.10
7 purchase totals =	$822.83		$883.9254	$883.93	$883.95	$884.00