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	$40.48	7.558%	$43.5395	$43.54	$43.55	$43.50
Purchase #2	$152.58	10.307%	$168.3064	$168.31	$168.30	$168.30
Purchase #3	$42.25	9.399%	$46.2211	$46.22	$46.20	$46.20
Purchase #4	$215.48	10.411%	$237.9136	$237.91	$237.90	$237.90
Purchase #5	$96.36	9.788%	$105.7917	$105.79	$105.80	$105.80
Purchase #6	$180.64	10.834%	$200.2105	$200.21	$200.20	$200.20
Purchase #7	$118.57	12.387%	$133.2573	$133.26	$133.25	$133.30
7 purchase totals =	$846.36		$935.2401	$935.24	$935.20	$935.20