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	$119.56	3.311%	$123.5186	$123.52	$123.50	$123.50
Purchase #2	$216.52	7.159%	$232.0207	$232.02	$232.00	$232.00
Purchase #3	$131.44	13.673%	$149.4118	$149.41	$149.40	$149.40
Purchase #4	$140.73	10.465%	$155.4574	$155.46	$155.45	$155.50
Purchase #5	$62.59	7.805%	$67.4751	$67.48	$67.50	$67.50
Purchase #6	$128.62	10.832%	$142.5521	$142.55	$142.55	$142.60
Purchase #7	$90.78	6.268%	$96.4701	$96.47	$96.45	$96.50
7 purchase totals =	$890.24		$966.9058	$966.91	$966.85	$967.00