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	$210.32	12.581%	$236.7804	$236.78	$236.80	$236.80
Purchase #2	$185.34	3.180%	$191.2338	$191.23	$191.25	$191.20
Purchase #3	$114.59	8.111%	$123.8844	$123.88	$123.90	$123.90
Purchase #4	$79.59	13.842%	$90.6068	$90.61	$90.60	$90.60
Purchase #5	$236.59	7.620%	$254.6182	$254.62	$254.60	$254.60
Purchase #6	$242.32	10.683%	$268.207	$268.21	$268.20	$268.20
Purchase #7	$55.62	13.635%	$63.2038	$63.20	$63.20	$63.20
7 purchase totals =	$1,124.37		$1,228.5344	$1,228.53	$1,228.55	$1,228.50