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	$58.53	4.625%	$61.237	$61.24	$61.25	$61.20
Purchase #2	$71.55	3.141%	$73.7974	$73.80	$73.80	$73.80
Purchase #3	$135.96	13.435%	$154.2262	$154.23	$154.25	$154.20
Purchase #4	$112.69	9.578%	$123.4834	$123.48	$123.50	$123.50
Purchase #5	$65.63	12.526%	$73.8508	$73.85	$73.85	$73.90
Purchase #6	$101.32	7.874%	$109.2979	$109.30	$109.30	$109.30
Purchase #7	$103.28	9.275%	$112.8592	$112.86	$112.85	$112.90
7 purchase totals =	$648.96		$708.7519	$708.76	$708.80	$708.80