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	$92.52	4.217%	$96.4216	$96.42	$96.40	$96.40
Purchase #2	$39.56	6.618%	$42.1781	$42.18	$42.20	$42.20
Purchase #3	$82.69	3.822%	$85.8504	$85.85	$85.85	$85.90
Purchase #4	$110.78	8.148%	$119.8064	$119.81	$119.80	$119.80
Purchase #5	$211.79	11.835%	$236.8553	$236.86	$236.85	$236.90
Purchase #6	$111.59	11.690%	$124.6349	$124.63	$124.65	$124.60
Purchase #7	$11.79	8.870%	$12.8358	$12.84	$12.85	$12.80
7 purchase totals =	$660.72		$718.5825	$718.59	$718.60	$718.60