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	$108.59	4.444%	$113.4157	$113.42	$113.40	$113.40
Purchase #2	$38.94	11.795%	$43.533	$43.53	$43.55	$43.50
Purchase #3	$51.79	8.782%	$56.3382	$56.34	$56.35	$56.30
Purchase #4	$231.98	6.641%	$247.3858	$247.39	$247.40	$247.40
Purchase #5	$25.36	9.582%	$27.79	$27.79	$27.80	$27.80
Purchase #6	$62.40	7.621%	$67.1555	$67.16	$67.15	$67.20
Purchase #7	$140.80	7.434%	$151.2671	$151.27	$151.25	$151.30
7 purchase totals =	$659.86		$706.8853	$706.90	$706.90	$706.90