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	$62.54	3.251%	$64.5732	$64.57	$64.55	$64.60
Purchase #2	$39.26	9.126%	$42.8429	$42.84	$42.85	$42.80
Purchase #3	$32.78	12.142%	$36.7601	$36.76	$36.75	$36.80
Purchase #4	$59.32	13.559%	$67.3632	$67.36	$67.35	$67.40
Purchase #5	$174.89	6.807%	$186.7948	$186.79	$186.80	$186.80
Purchase #6	$5.71	13.260%	$6.4671	$6.47	$6.45	$6.50
Purchase #7	$149.46	11.416%	$166.5224	$166.52	$166.50	$166.50
7 purchase totals =	$523.96		$571.3237	$571.31	$571.25	$571.40