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	$183.33	5.825%	$194.009	$194.01	$194.00	$194.00
Purchase #2	$116.32	13.356%	$131.8557	$131.86	$131.85	$131.90
Purchase #3	$108.26	8.653%	$117.6277	$117.63	$117.65	$117.60
Purchase #4	$59.51	10.735%	$65.8984	$65.90	$65.90	$65.90
Purchase #5	$240.61	9.749%	$264.0671	$264.07	$264.05	$264.10
Purchase #6	$166.76	12.383%	$187.4099	$187.41	$187.40	$187.40
Purchase #7	$16.75	9.580%	$18.3547	$18.35	$18.35	$18.40
7 purchase totals =	$891.54		$979.2225	$979.23	$979.20	$979.30