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	$51.63	4.351%	$53.8764	$53.88	$53.90	$53.90
Purchase #2	$242.73	10.127%	$267.3113	$267.31	$267.30	$267.30
Purchase #3	$169.86	9.210%	$185.5041	$185.50	$185.50	$185.50
Purchase #4	$117.87	11.225%	$131.1009	$131.10	$131.10	$131.10
Purchase #5	$17.78	6.242%	$18.8898	$18.89	$18.90	$18.90
Purchase #6	$148.52	5.561%	$156.7792	$156.78	$156.80	$156.80
Purchase #7	$60.25	8.788%	$65.5448	$65.54	$65.55	$65.50
7 purchase totals =	$808.64		$879.0065	$879.00	$879.05	$879.00