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	$68.92	6.301%	$73.2626	$73.26	$73.25	$73.30
Purchase #2	$103.29	9.268%	$112.8629	$112.86	$112.85	$112.90
Purchase #3	$226.86	4.738%	$237.6086	$237.61	$237.60	$237.60
Purchase #4	$199.64	4.139%	$207.9031	$207.90	$207.90	$207.90
Purchase #5	$42.28	3.191%	$43.6292	$43.63	$43.65	$43.60
Purchase #6	$65.85	8.431%	$71.4018	$71.40	$71.40	$71.40
Purchase #7	$170.38	8.740%	$185.2712	$185.27	$185.25	$185.30
7 purchase totals =	$877.22		$931.9394	$931.93	$931.90	$932.00