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	$165.76	6.554%	$176.6239	$176.62	$176.60	$176.60
Purchase #2	$73.43	9.800%	$80.6261	$80.63	$80.65	$80.60
Purchase #3	$99.86	9.803%	$109.6493	$109.65	$109.65	$109.60
Purchase #4	$96.67	5.362%	$101.8534	$101.85	$101.85	$101.90
Purchase #5	$31.50	7.174%	$33.7598	$33.76	$33.75	$33.80
Purchase #6	$199.47	8.556%	$216.5367	$216.54	$216.55	$216.50
Purchase #7	$119.75	7.204%	$128.3768	$128.38	$128.40	$128.40
7 purchase totals =	$786.44		$847.4260	$847.43	$847.45	$847.40