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	$134.67	5.781%	$142.4553	$142.46	$142.45	$142.50
Purchase #2	$169.25	4.478%	$176.829	$176.83	$176.85	$176.80
Purchase #3	$195.44	7.191%	$209.4941	$209.49	$209.50	$209.50
Purchase #4	$193.82	12.715%	$218.4642	$218.46	$218.45	$218.50
Purchase #5	$129.81	5.674%	$137.1754	$137.18	$137.20	$137.20
Purchase #6	$84.81	6.533%	$90.3506	$90.35	$90.35	$90.40
Purchase #7	$106.97	9.149%	$116.7567	$116.76	$116.75	$116.80
7 purchase totals =	$1,014.77		$1,091.5253	$1,091.53	$1,091.55	$1,091.70