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	$103.69	5.661%	$109.5599	$109.56	$109.55	$109.60
Purchase #2	$81.50	5.685%	$86.1333	$86.13	$86.15	$86.10
Purchase #3	$150.29	12.179%	$168.5938	$168.59	$168.60	$168.60
Purchase #4	$109.64	13.206%	$124.1191	$124.12	$124.10	$124.10
Purchase #5	$169.91	6.442%	$180.8556	$180.86	$180.85	$180.90
Purchase #6	$162.37	10.570%	$179.5325	$179.53	$179.55	$179.50
Purchase #7	$234.50	5.460%	$247.3037	$247.30	$247.30	$247.30
7 purchase totals =	$1,011.90		$1,096.0979	$1,096.09	$1,096.10	$1,096.10